RFR(XS) : 8187020 : AOT tests should not fail if devkit dependency isn't resolved

[Igor Ignatyev]

http://cr.openjdk.java.net/~iignatyev//8187020/webrev.00/index.html
> 11 lines changed: 5 ins; 0 del; 6 mod;

Hi all,

could you please review this tiny fix or AOT tests? Prior this fix, the tests would fail w/ FileNotFoundException when devkit dependency can't be resolved even if jaotc is able to find a linker, e.g. in one of VS*COMNTOOLS. after this fix, if tests aren't able to download devkit, they will allow jaotc to try to find a linker. This patch also remove search for 'ld' in PATH on windows b/c jaotc doesn't use it on windows.

webrev: http://cr.openjdk.java.net/~iignatyev//8187020/webrev.00/index.html
jbs: https://bugs.openjdk.java.net/browse/JDK-8187020
testing: compiler/aot tests

Thanks,
-- Igor