RFR: add simple test workflow

[Jonathan Gibbons]

On Fri, 9 Jul 2021 22:14:19 GMT, Igor Ignatyev <iignatyev at openjdk.org> wrote:

> Hi all,
> 
> could you please review this small patch that adds a simple github action workflow to build and test `jtreg` on `linux-x64`?
> 
> Thanks,
> -- Igor

Changes requested by jjg (Lead).

.github/workflows/test.yml line 23:

> 21:         working-directory: jtreg
> 22:         shell: bash
> 23:         run: sh make/build-all.sh ${JAVA_HOME_8_X64}

needs to be `make/build.sh`  

`make/build-all.sh` is obsolete and should now be deleted.

.github/workflows/test.yml line 39:

> 37:              HEADLESS=1
> 38:              JDK8_HOME=${JAVA_HOME_8_X64}
> 39:              sh make/build-all.sh ${JAVA_HOME_8_X64}

use `make/build.sh`

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PR: https://git.openjdk.java.net/jtreg/pull/16