RFR: JDK-8150203 Incremental update from build-infra project

Fri Feb 19 15:51:18 UTC 2016

More incremental fixes from the build-infra project. The list of fixes 
include:

* More ExecuteWithLog.
* Native buildtools fixes.
* Make DTDParser quiet.
* LIBM cleanups.
* Export LDFLAGS_HASH_STYLE.
* Remove superfluous -export on LDFLAGS_windows. (JNIEXPORT used)
* Don't let make reconfigure delete spec.gmk on abort

I have run this using JPRT and the COMPARE_BUILD functionality, which 
shows no differences. I'm still awaiting results from the last 
platforms, but so far it's looking good. (I'll report back if something 
breaks.)

Bug: https://bugs.openjdk.java.net/browse/JDK-8150203
WebRev: 
http://cr.openjdk.java.net/~ihse/JDK-8150203-incremental-build-infra-fixes/webrev.01

/Magnus