RFR: JDK-8198318 Make build comparisons clean again

[Tim Bell]

Magnus:

> Over time, small differences has accumulated in the build that makes it
> non-reproducible. This patch addresses some of these, and modifies
> compare.sh to properly handles those that cannot be fixed.
>
> This patch is mainly due to Erik, who wrote most of it. I've mostly
> finished it up.
>
> Bug: https://bugs.openjdk.java.net/browse/JDK-8198318
> WebRev:
> http://cr.openjdk.java.net/~ihse/JDK-8198318-make-build-comparisons-clean-again/webrev.01

One typo:
make/common/MakeBase.gmk
  548         # Work around a weirdness with cp on Macosx. When coying a 
symlink, if

Should be 'when copying'.  No need to respin the webrev.

Looks good otherwise.

/Tim