[ELF] - Allow using PLT relocations when "-z notext" is given.

This is part of PR35720.

Currently LLD allows dynamic relocations against text when -z notext is given.
Though for non-PIC relocations like R_X86_64_PC32 that does not work,
we produce "relocation R_X86_64_PC32 cannot be used against shared object;"
error because they may overflow in runtime.

Solution implemented is to use PLT for them.

Differential revision: https://reviews.llvm.org/D41541

llvm-svn: 321400