RFR (S): JDK-8142909 Integration of minor fixes from the build-infra project

[Magnus Ihse Bursie]

In the new hotspot build project, we have made a few changes to the 
existing build. In preparation for the new build, I'd like to integrate 
these into mainline.

These changes are:
* When overriding optimization, do not lose current debug (-g) setting (!)
* Make adlc actually quiet in quiet mode
* Make g1EvacStats.cpp compile in all cases without precompiled headers
* Sort saproc object files when linking (facilitates comparison to new 
build)

Unless someone suggests otherwise, I intend to push this (using JPRT) to 
hs-rt.

Bug: https://bugs.openjdk.java.net/browse/JDK-8142909
WebRev: 
http://cr.openjdk.java.net/~ihse/JDK-8142909-hotspot-build-infra-integration/webrev.01

/Magnus