[ELF] - Ignore non-absolute R_386_GOTPC relocation in debug sections.

This is for PR34852.

GCC 8.0 or earlier have a bug that it emits R_386_GOTPC relocations
against _GLOBAL_OFFSET_TABLE for .debug_info. The bug seems to have
been fixed in 2017: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82630,
but we do not want LLD to report errors for such inputs.
In this patch we ignore such relocations.

Differential revision: https://reviews.llvm.org/D38625

llvm-svn: 316761