When I run a full JDK9 build, including the install directory, I get the following error:

-----------------------------------------------------------------------------------
## Starting installer
...
Sanity check passed.
+ command -v nproc
/usr/bin/nproc
+ nproc
+ processor_count=4
+ min_job_count=2
+ max_job_count=5
/localhome/kcr/java/jdk9-client/install/make/smartmake//compile_async.sh: 35: /localhome/kcr/java/jdk9-client/install/make/smartmake//compile_async.sh: Syntax error: "(" unexpected
make[2]: *** [/localhome/kcr/java/jdk9-client/build/linux-x86_64-normal-server-release/install/lib/libcommon.a] Error 2
make[1]: *** [/localhome/kcr/java/jdk9-client/build/linux-x86_64-normal-server-release/install/_install.timestamp] Error 2
Reaping losing child 0x01c510a0 PID 4948
Removing child 0x01c510a0 PID 4948 from chain.
Reaping losing child 0x00b58750 PID 4919
make: *** [installer-only] Error 2
Removing child 0x00b58750 PID 4919 from chain.
-----------------------------------------------------------------------------------

The reason for the failure is that the script relies on bash features that are not standard POSIX shell features supported by the default "dash" shell. On Ubuntu Linux /bin/sh is sym-linked to /bin/dash so specifying "sh myscript.sh" will run the dash shell. The script in question does specify:

#!/bin/bash

so it is intended to be executed by bash, but something in the Makefile is specifying "sh" or "/bin/sh" explicitly.