Remove the TUNE_FEATURES references from go_map_arch,
to avoid an unwanted variable dependency. Direct
comparisons of the architecture name are sufficient
for covering what Go currently supports, and using
TUNE_CCARGS_remove adequately handles the conflict
with the cgo-supplied flags for mips.
Signed-off-by: Matt Madison <matt@madison.systems> Signed-off-by: Ross Burton <ross.burton@intel.com>
