Maybe one generic function (called e.g. tc-set-linker) whose arguments are a preference-ordered list of supported linkers? If currently used linker is not in the specified list, then this function would force using first found linker from that list.
Forcing bfd only: tc-set-linker bfd Forcing gold only: tc-set-linker gold Forcing lld only: tc-set-linker lld Forcing bfd or gold (with bfd preferred if both are available): tc-set-linker bfd gold Forcing bfd or lld (with bfd preferred if both are available): tc-set-linker bfd lld Forcing lld or bfd (with lld preferred if both are available): tc-set-linker lld bfd
