Add ELF relocations for the following Thumb fixups:
- fixup_thumb_adr_pcrel_10 -> R_ARM_THM_PC8
- fixup_thumb_cp -> R_ARM_THM_PC8
- fixup_t2_adr_pcrel_12 -> R_ARM_THM_PREL_11_0
- fixup_t2_ldst_pcrel_12 -> R_ARM_THM_PC12
While these relocations are short-ranged there is support in the open source ELF linker's in binutils and soon to be in LLD. MC (D72197) will no longer resolve pc-relative fixups to global symbols due to interpositioning concerns, which results in an error message. I have a patch implementing these three relocations in LLD ready to submit.
TODO: Connect up the ARM state relocations for the pc-relative adr and ldr fixups. These will come in a follow-up patch when I have LLD support ready.
Part of the long term fix for pr44929 https://bugs.llvm.org/show_bug.cgi?id=44929