I'm doing openjdk development on Raspberry Pi OS 32-bit (linux-arm) and see skara cli failing. Recipe:

 $ ( rm -rf skara && git clone --no-progress https://github.com/openjdk/skara.git && git config --global include.path "$PWD/skara/skara.gitconfig" && git skara update )
Cloning into 'skara'...
  1.87s user 0.64s system 125% cpu 2.010 total
Compiling ...
Downloading Gradle...
  % Total % Received % Xferd Average Speed Time Time Time Current
                                 Dload Upload Total Spent Left Speed
  0 0 0 0 0 0 0 0 --:--:-- --:--:-- --:--:-- 0
  0 0 0 0 0 0 0 0 --:--:-- --:--:-- --:--:-- 0
 45 107M 45 49.0M 0 0 53.1M 0 0:00:02 --:--:-- 0:00:02 53.1M
100 107M 100 107M 0 0 58.9M 0 0:00:01 0:00:01 --:--:-- 64.9M
Extracting Gradle...

FAILURE: Build failed with an exception.

* What went wrong:
Supplied javaHome must be a valid directory. You supplied: /home/martin/ws/skara/bin/image
...

---

Having built skara on linux-x86_64, I notice it didn't try to download a JDK - **it should explain that**. Raspberry Pi OS is the most important computing platform for the next generation of developers, so it's disappointing (if understandable) that openjdk does not provide official arm-32 binaries. But adoptopenjdk does provide such binaries. Let's try taking that hint in the error message and installing a jdk14, as suggested at https://github.com/openjdk/skara:

 $ ( rm -rf skara && git clone --no-progress https://github.com/openjdk/skara.git && git config --global include.path "$PWD/skara/skara.gitconfig" && mkdir -p skara/bin/image && rsync -a $(jver 14)/ skara/bin/image/ && git skara update )
Cloning into 'skara'...
  1.94s user 0.51s system 122% cpu 1.992 total
  2.56s user 3.09s system 144% cpu 3.914 total
Compiling ...
Downloading Gradle...
  % Total % Received % Xferd Average Speed Time Time Time Current
                                 Dload Upload Total Spent Left Speed
  0 0 0 0 0 0 0 0 --:--:-- --:--:-- --:--:-- 0
  0 0 0 0 0 0 0 0 --:--:-- --:--:-- --:--:-- 0
 10 107M 10 11.5M 0 0 27.4M 0 0:00:03 --:--:-- 0:00:03 27.4M
 69 107M 69 74.7M 0 0 52.7M 0 0:00:02 0:00:01 0:00:01 63.3M
100 107M 100 107M 0 0 56.0M 0 0:00:01 0:00:01 --:--:-- 64.0M
Extracting Gradle...
Starting a Gradle Daemon, 1 busy and 2 incompatible Daemons could not be reused, use --status for details
Watching the file system is not supported on this operating system.
> Task :skara-proxy:compileJava
> Task :skara-version:compileJava
> Task :skara-reproduce:compileJava
> Task :skara-module:compileJava
> Task :skara-reproduce:pluginDescriptors
> Task :skara-module:pluginDescriptors
> Task :skara-version:pluginDescriptors
> Task :skara-version:processResources
> Task :skara-module:processResources
> Task :skara-module:classes
> Task :skara-version:classes
> Task :skara-reproduce:processResources
> Task :skara-reproduce:classes
> Task :skara-module:jar
> Task :skara-reproduce:jar
> Task :skara-version:jar
> Task :skara-proxy:pluginDescriptors
> Task :skara-proxy:processResources
> Task :skara-proxy:classes
> Task :skara-proxy:jar
> Task :skara-images:compileJava
> Task :skara-images:pluginDescriptors
> Task :skara-images:processResources
> Task :skara-images:classes
> Task :skara-images:jar
> Task :census:processResources NO-SOURCE
> Task :cli:launchersLocal
> Task :xml:compileJava
> Task :xml:processResources NO-SOURCE
> Task :xml:classes
> Task :xml:jar
> Task :ini:compileJava
> Task :ini:processResources NO-SOURCE
> Task :ini:classes
> Task :ini:jar
> Task :email:compileJava
> Task :email:processResources NO-SOURCE
> Task :email:classes
> Task :email:jar
> Task :args:compileJava
> Task :args:processResources NO-SOURCE
> Task :args:classes
> Task :args:jar
> Task :network:processResources NO-SOURCE
> Task :census:compileJava
> Task :census:classes
> Task :census:jar
> Task :metrics:compileJava
> Task :metrics:processResources NO-SOURCE
> Task :metrics:classes
> Task :metrics:jar
> Task :vcs:processResources
> Task :host:processResources NO-SOURCE
> Task :issuetracker:processResources NO-SOURCE
> Task :forge:processResources NO-SOURCE
> Task :jbs:processResources NO-SOURCE
> Task :jcheck:processResources NO-SOURCE
> Task :encoding:compileJava
> Task :encoding:processResources NO-SOURCE
> Task :encoding:classes
> Task :encoding:jar
> Task :json:compileJava
> Task :json:processResources NO-SOURCE
> Task :json:classes
> Task :process:compileJava
> Task :process:processResources NO-SOURCE
> Task :process:classes
> Task :process:jar
> Task :json:jar
> Task :version:compileJava
> Task :version:processResources NO-SOURCE
> Task :version:classes
> Task :version:jar
> Task :webrev:processResources
> Task :cli:processResources NO-SOURCE
> Task :proxy:compileJava
> Task :proxy:processResources NO-SOURCE
> Task :proxy:classes
> Task :proxy:jar
> Task :network:compileJava
> Task :network:classes
> Task :network:jar
> Task :vcs:compileJava
> Task :vcs:classes
> Task :vcs:jar
> Task :host:compileJava
> Task :host:classes
> Task :host:jar
> Task :issuetracker:compileJava
> Task :issuetracker:classes
> Task :issuetracker:jar

> Task :forge:compileJava
/home/martin/ws/skara/forge/src/main/java/org/openjdk/skara/forge/github/GitHubRepository.java:474: error: : expected
                                 case "cancelled" -> checkBuilder.cancel(completedAt);
                                                 ^
/home/martin/ws/skara/forge/src/main/java/org/openjdk/skara/forge/github/GitHubRepository.java:474: error: illegal start of expression
                                 case "cancelled" -> checkBuilder.cancel(completedAt);
                                                  ^
/home/martin/ws/skara/forge/src/main/java/org/openjdk/skara/forge/github/GitHubRepository.java:475: error: : expected
                                 case "success" -> checkBuilder.complete(true, completedAt);
                                               ^
/home/martin/ws/skara/forge/src/main/java/org/openjdk/skara/forge/github/GitHubRepository.java:475: error: illegal start of expression
                                 case "success" -> checkBuilder.complete(true, completedAt);
                                                ^
/home/martin/ws/skara/forge/src/main/java/org/openjdk/skara/forge/github/GitHubRepository.java:476: error: : expected
                                 case "action_required", "failure", "neutral" -> checkBuilder.complete(false, completedAt);
                                                       ^
/home/martin/ws/skara/forge/src/main/java/org/openjdk/skara/forge/github/GitHubRepository.java:477: error: : expected
                                 case "skipped" -> checkBuilder.skipped(completedAt);
                                               ^
/home/martin/ws/skara/forge/src/main/java/org/openjdk/skara/forge/github/GitHubRepository.java:477: error: illegal start of expression
                                 case "skipped" -> checkBuilder.skipped(completedAt);
                                                ^
/home/martin/ws/skara/forge/src/main/java/org/openjdk/skara/forge/github/GitHubRepository.java:478: error: : expected
                                 default -> throw new IllegalStateException("Unexpected conclusion: " + conclusion);
                                        ^
/home/martin/ws/skara/forge/src/main/java/org/openjdk/skara/forge/github/GitHubRepository.java:478: error: illegal start of expression
                                 default -> throw new IllegalStateException("Unexpected conclusion: " + conclusion);
                                         ^
/home/martin/ws/skara/forge/src/main/java/org/openjdk/skara/forge/github/GitHubPullRequest.java:412: error: : expected
                                    case "cancelled" -> checkBuilder.cancel(completedAt);
                                                    ^
/home/martin/ws/skara/forge/src/main/java/org/openjdk/skara/forge/github/GitHubPullRequest.java:412: error: illegal start of expression
                                    case "cancelled" -> checkBuilder.cancel(completedAt);
                                                     ^
/home/martin/ws/skara/forge/src/main/java/org/openjdk/skara/forge/github/GitHubPullRequest.java:413: error: : expected
                                    case "success" -> checkBuilder.complete(true, completedAt);
                                                  ^
/home/martin/ws/skara/forge/src/main/java/org/openjdk/skara/forge/github/GitHubPullRequest.java:413: error: illegal start of expression
                                    case "success" -> checkBuilder.complete(true, completedAt);
                                                   ^
/home/martin/ws/skara/forge/src/main/java/org/openjdk/skara/forge/github/GitHubPullRequest.java:414: error: : expected
                                    case "action_required", "failure", "neutral" -> checkBuilder.complete(false, completedAt);
                                                          ^
/home/martin/ws/skara/forge/src/main/java/org/openjdk/skara/forge/github/GitHubPullRequest.java:415: error: : expected
                                    case "skipped" -> checkBuilder.skipped(completedAt);
                                                  ^
/home/martin/ws/skara/forge/src/main/java/org/openjdk/skara/forge/github/GitHubPullRequest.java:415: error: illegal start of expression
                                    case "skipped" -> checkBuilder.skipped(completedAt);
                                                   ^
/home/martin/ws/skara/forge/src/main/java/org/openjdk/skara/forge/github/GitHubPullRequest.java:416: error: : expected
                                    default -> throw new IllegalStateException("Unexpected conclusion: " + conclusion);
                                           ^
/home/martin/ws/skara/forge/src/main/java/org/openjdk/skara/forge/github/GitHubPullRequest.java:416: error: illegal start of expression
                                    default -> throw new IllegalStateException("Unexpected conclusion: " + conclusion);
                                            ^

> Task :jcheck:compileJava
> Task :jcheck:classes
> Task :webrev:compileJava
> Task :webrev:classes
> Task :jcheck:jar
> Task :webrev:jar
> Task :jbs:compileJava
> Task :jbs:classes
> Task :jbs:jar

> Task :forge:compileJava
18 errors

> Task :forge:compileJava FAILED

FAILURE: Build failed with an exception.

* What went wrong:
Execution failed for task ':forge:compileJava'.

---

It sure looks like jdk 14 is insufficient for building skara (in retrospect, a red herring!)