DataFlowSanitizer: wrappers of functions with local linkage should have the...

DataFlowSanitizer: wrappers of functions with local linkage should have the same linkage as the function being wrapped

This patch resolves link errors when the address of a static function is taken, and that function is uninstrumented by DFSan.

This change resolves bug 36314.

Patch by Sam Kerner!

Differential Revision: https://reviews.llvm.org/D44784

llvm-svn: 328890