issues compiling adlc

[Johan Vos]

When building the latest with XCode 7.3.1 I ran into the issue that
hotspot/src/share/vm/adlc/adlparse.cpp could not be compiled due to an
"Unsupported architecture".
It seems that there the flags that are passed with the other compile tasks
(e.g. -arch arm64) are not passed for this file.
When I add -arch arm64 to the clang++ task, it works.

I also notice that CompileJvm.gmk defines
JVM_EXCLUDES +=adlc
EXCLUDES := $(JVM_EXCLUDES)

But I'm not sure this indicates adlc should not be compiled at all, or just
not included in libraries.

- Johan