[DebugInfo] Fine tune emitting flags as part of the producer

When using APPLE extensions, don't duplicate the compiler invocation's
flags both in AT_producer and AT_APPLE_flags.

Differential revision: https://reviews.llvm.org/D50453

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@339268 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed