[modules] Fix a rejects-valid resulting from emitting an inline function
recursively within the emission of another inline function. This ultimately
led to us emitting the same inline function definition twice, which we then
rejected because we believed we had a mangled name conflict.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@215579 91177308-0d34-0410-b5e6-96231b3b80d8