[GCOV] Avoid emitting profile arcs for module and skeleton CUs

Do not emit profile arc files and note files for module and skeleton
CU's.

Our users report seeing unexpected *.gcda and *.gcno files in their
projects when using gcov-style profiling with modules or frameworks.
The unwanted files come from these modules. This is not very helpful
for end-users. Further, we've seen reports of instrumented programs
crashing while writing these files out (due to I/O failures).

rdar://problem/22838296

Reviewed-by: aprantl

Differential Revision: http://reviews.llvm.org/D15997

llvm-svn: 258406