Don't emit the extra checksum into the .gcda file if the user hasn't asked for
it. Fortunately, versions of gcov that predate the extra checksum also ignore
any extra data, so this isn't a problem. There will be a matching commit in
compiler-rt.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@176745 91177308-0d34-0410-b5e6-96231b3b80d8