RFR: JDK-8143141: Bring in minor build changes from the jigsaw/jake forest

[Mandy Chung]

> On Nov 17, 2015, at 7:11 AM, Erik Joelsson <erik.joelsson at oracle.com> wrote:
> 
> Hello,
> 
> When bringing changes from jdk9 to jigsaw/jake, the merges have become quite involved. The build files in jdk9 and jake have also diverged unnecessarily over time. I would like to bring them back closer to each other so that we are only carrying the changes we really need to in jake.
> 

Thanks for doing this, Erik.   It’d be good to bring back such changes to jdk9/dev.  They are good cleanup.

> New webrevs, only for top and jdk now. The other repos no longer need changes:
> http://cr.openjdk.java.net/~erikj/8143141/webrev.top.02/
> http://cr.openjdk.java.net/~erikj/8143141/webrev.jdk.02/

I skimmed on it and looks okay.   One question:

 526 JAVAC_FLAGS := -bootclasspath $(EMPTY_DIR) -extdirs \
 527     $(EMPTY_DIR) -endorseddirs $(EMPTY_DIR) $($(MODULE)_ADD_JAVAC_FLAGS)
 528 

What -target option is used together with these javac flags?  I suppose -target 8 in order to get the boot cycle build work.

Mandy