RFR: 8256393: Github Actions build on Linux should define OS and GCC versions

[Tiago Daitx]

Hi,


> >> 89:
> >> 90:       - name: Build jtreg
> >> 91:         run: sh make/build-all.sh ${JAVA_HOME_8_X64}
> >
> > What is this change?
>
> On ubuntu-20.04 the default Java installation is now set to 11, but jtreg still requires Java 8 for building.

Why does jtreg need OpenJDK-8 for building? On Debian/Ubuntu we have
been using the 'release' parameter to build jtreg using OpenJDK 11
while maintaining OpenJDK 8 compatibility. See
https://sources.debian.org/src/jtreg/5.1-b01-2/debian/patches/use-release-instead-of-source-target.patch/
for how we do it.

Please note that while we replace "source/target" for "release", one
can specify both "source/target" and "release" for a javac task: ant
is smart enough to pick one and ignore the other, depending on it
being run on JDK9+ or not. See 'release' description at
https://ant.apache.org/manual/Tasks/javac.html

Cheers!

-- 
Tiago Stürmer Daitx
Software Engineer
tiago.daitx at canonical.com

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