When building a module, use the macro definitions on the command line

When building a module, use the macro definitions on the command line
as part of the hash rather than ignoring them. This means we'll end up
building more module variants (overall), but it allows configuration
macros such as NDEBUG to work so long as they're specified via command
line. More to come in this space.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@142187 91177308-0d34-0410-b5e6-96231b3b80d8