RFR: add simple test workflow [v2]

[Igor Ignatyev]

> 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

Igor Ignatyev has updated the pull request incrementally with two additional commits since the last revision:

 - use bash instead of sh to run make/build.sh
 - use make/build.sh
   s/JDK8_HOME/JDK8HOME

-------------

Changes:
  - all: https://git.openjdk.java.net/jtreg/pull/16/files
  - new: https://git.openjdk.java.net/jtreg/pull/16/files/bdaec077..9af81193

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jtreg&pr=16&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jtreg&pr=16&range=00-01

  Stats: 4 lines in 1 file changed: 0 ins; 1 del; 3 mod
  Patch: https://git.openjdk.java.net/jtreg/pull/16.diff
  Fetch: git fetch https://git.openjdk.java.net/jtreg pull/16/head:pull/16

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