RFR JDK-8217761: Enhance run-test-prebuilt jib profile to support running tests with JCov

[Magnus Ihse Bursie]

If you are going down this road, you'll need to verify that JCOV_IMAGE_DIR is not empty in RunTests. So keep the ifneq statement, but with an $(error ...) instead. Otherwise we'll just fail spectacularly and incomprehensible later on. 

/Magnus

> 28 jan. 2019 kl. 18:47 skrev Erik Joelsson <erik.joelsson at oracle.com>:
> 
> Hello Shura,
> 
> In RunTest.gmk, you removed the conditional, but the comment still implies that it's there. Please update the comment. Otherwise this looks good!
> 
> /Erik
> 
>> On 2019-01-25 15:20, Alexandre (Shura) Iline wrote:
>> Hi,
>> 
>> Please take a look on a change to allow JCov test execution through jib.
>> 
>> Please notice that this fix also changes behavior of RunTest.gmk when conflicting combination of options is used. JCOV_IMAGE_DIR  is now expected to be set when TEST_OPTS_JCOV is true.
>> 
>> Shura
>> 
>> Bug: https://bugs.openjdk.java.net/browse/JDK-8217761
>> Webrev: http://cr.openjdk.java.net/~shurailine/8217761/webrev.02/