cmd/link/internal/ppc64: link ELFv2 objects built with -mcpu=power10
Specifically, objects built via cgo using CGO_CFLAGS="-O2 -g -mcpu=power10".
These use new relocations defined by ELFv2 1.5, and the R_PPC64_REL24_NOTOC
relocation. These objects contain functions which may not use a TOC
pointer requiring the insertion of trampolines to use correctly.
The relocation targets of these ELFv2 objects may also contain non-zero
values. Clear the relocated bits before setting them.
Extra care is taken if GOPPC64 < power10. The R_PPC64_REL24_NOTOC reloc
existed prior to ELFv2 1.5. The presence of this relocation itself does
not imply a power10 target. Generate power8 compatible stubs if
GOPPC64 < power10.