It is visible in current GHA runs that building jtreg in all worker at once sometimes break on dependencies checkout, for example:

[build.sh][INFO] CYGWIN_OR_MSYS=0
[build.sh][INFO] JAVA_HOME: /usr/lib/jvm/temurin-17-jdk-amd64
[build.sh][INFO] Downloading https://archive.apache.org/dist/ant/binaries/apache-ant-1.10.8-bin.zip to /home/runner/work/jdk/jdk/jtreg/src/make/../build/deps/apache-ant-1.10.8-bin.zip
Error: sh][ERROR] wget exited with exit code 4
Error: Process completed with exit code 1.

I suppose this is a side-effect of pulling lots of dependencies all at once. Additionally, we often had problems with building jtreg on various platforms. We do not have to build jtreg for every platform. We can just have a job step that does it once, and stores it in the cache for all dependent jobs to use.

It would also save some build time across various jobs.