RFR: JDK-8166648,,jib make run-test for langtools results in intermittent failures on windows-x86

[Tim Bell]

Hello

The change of HotSpot runtimes on 32-bit Windows [1] has been a source 
of langtools test failures due to memory space exhaustion.

On our Windows build/test clients, the combination of the C2 runtime and 
parallel GC causes about 20 extra threads to be started in each VM. 
These added thread stacks, plus heap management in C2, result in too 
much memory pressure to fit the workload into 32-bit VMs.

This fix will run langtools jtreg tests using the serial garbage 
collector instead of using the default collector (parallel GC).

Testing:
    -5 out of 5 jobs (with the fix) passed langtools testing
    -4 out of 5 control jobs (without the fix) failed testing in 
windows_i586_6.3-product-c2-langtools_jtreg


Thanks in advance-

Tim

[1] JDK-8154209 "Remove client VM from default JIB profile on 
windows-x86 and linux-x86"
https://bugs.openjdk.java.net/browse/JDK-8154209