[ELF] - Check we able to report function symbols that encloses a location in error messages.

InputSectionBase::getLocation() have the following block of the code which
is uncovered by our test cases:
https://github.com/llvm-mirror/lld/blob/master/ELF/InputSection.cpp#L238

Patch adds a test to trigger this branch.

llvm-svn: 337256