RFR: 8028498: runtime/SharedArchiveFile/CdsDifferentObjectAlignment.java asserts in RT_Baseline

[Stefan Johansson]

Hi,

Please review this fix for:
https://bugs.openjdk.java.net/browse/JDK-8028498

Webrev:
http://cr.openjdk.java.net/~sjohanss/8028498/webrev.00/

Summary:
The initial young generation size has been fairly small by default 
(1.5M) and if setting ObjectAlignmentInBytes to something larger than 
the default it can causes CDS to trigger a GC when dumping the archive. 
At this point the VM is not ready to handle a GC and we will hit an 
assertion. Making sure we can handle a GC at this point is not trivial 
and the proposed solution is to alter the default sizing of the young 
generation as well as adding a safety check when dumping the archive to 
exit the VM if the young generation is too small.

Testing:
* JPRT build and test passes
* Failing test now passes on all platforms (tested throught JPRT)
* Verified that the GC and Runtime jtreg tests still passes

Cheers,
Stefan