[LLD][ELF] - Update test case to check the error message reported. NFC.
[LLD][ELF] - Update test case to check the error message reported. NFC.

This updates znotext-plt-relocations-protected.s test case
(adds a file symbol) to check how the error message is built.

It allows to cover/test the following line:
https://github.com/llvm-mirror/lld/blob/master/ELF/Relocations.cpp#L79

git-svn-id: f6089bf0e6284f307027cef4f64114ee9ebb0424@339550 91177308-0d34-0410-b5e6-96231b3b80d8

llvm-mirror/lld,llvm-mirror/lld