Define MCAsmBackend::shouldForceRelocation
Return true if the MCValue has a specifier. When a relocation specifier
is specified, GNU Assembler will generate a relocation unless the
specifier can be optimized due to target-specific reasons (e.g. PPC `@l`
`@ha`).
This reduces targets' reliance on a MCAssembler::evaluateFixup hack
`if (Target.SymSpecifier || SA.isUndefined()) {`, previosuly
`if (A->getKind() != MCSymbolRefExpr::VK_None || SA.isUndefined()) {`
llvm/test/MC/SystemZ/fixups.s is known to rely on this hack.
