X86: refactor export directive generation

Create a helper function to generate the export directive.  This was previously
duplicated inline to handle export directives for variables and functions.  This
also enables the use of range-based iterators for the generation of the
directive rather than the traditional loops.  NFC.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@207925 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed