Only check for matching arch and UUID when looking for dsym in vincinity of executable.

ModuleSpecs::FindMatchingModuleSpec looks for matching filenames but when
looking for the dSYM we should only be looking for a matching architecture and
and UUID. Jason pointed out this mistake in http://reviews.llvm.org/D9174 when
this function was incorrectly converted to not be Mac specific.

Test Plan:
Running LLDB on test/lang/c/shared_lib_stripped_symbols/a.out in a debugger I've
verified LocateDSYMInVincinityOfExecutable correctly locates the matching dSYM.

Differential Revision: http://reviews.llvm.org/D9896

llvm-svn: 237907