ix86: restrict use of GOT32X relocs

The ELF linker rejects use of this reloc type without a base register
for PIC code. Suppress its use by gas in such cases.

To keep things building for non-ELF, include the entire containing if()
in an #ifdef: All consumers of ->fx_tcbit* live in such conditionals as
well, hence there's no reason to keep the producer active.
4 files changed