build-baremetal and build-crosstool-ng: make -A work, move arch check to common

build-baremetal

@@ -9,10 +9,11 @@ class Main(common.BuildCliFunction):
         super().__init__(
             description='''\
 Build the baremetal examples with crosstool-NG.
-''')
+''',
+            supported_archs=common.consts['crosstool_ng_supported_archs']
+        )
 
     def build(self):
-        self.assert_crosstool_ng_supports_arch(self.env['arch'])
         build_dir = self.get_build_dir()
         bootloader_obj = os.path.join(self.env['baremetal_build_lib_dir'], 'bootloader{}'.format(self.env['obj_ext']))
         common_basename_noext = 'common'