outmacho: always use symbol-relative relocations for MachO64
outmacho: always use symbol-relative relocations for MachO64

It seems that the MachO64 linker really doesn't like segment-relative
relocations under certain circumstances, so force relocations to be converted
to "external" (symbol-relative); error out if no symbol is available
(if this is a problem, we can consider inserting a synthetic symbol if
necessary.)

Signed-off-by: H. Peter Anvin <8a453bad9912ffe59bc0f0b8abe03df9be19379e@linux.intel.com>

techkey/nasm,techkey/nasm,techkey/nasm,techkey/nasm,techkey/nasm