[Features] Allow ExtensionMacros to be enabled in noasserts builds.

Author: hborla

include/swift/Basic/Features.def

@@ -123,7 +123,7 @@ EXPERIMENTAL_FEATURE(CodeItemMacros, false)
 EXPERIMENTAL_FEATURE(TupleConformances, false)
 EXPERIMENTAL_FEATURE(InitAccessors, false)
 
-EXPERIMENTAL_FEATURE(ExtensionMacros, false)
+EXPERIMENTAL_FEATURE(ExtensionMacros, true)
 SUPPRESSIBLE_LANGUAGE_FEATURE(ExtensionMacroAttr, 0, "@attached(extension)", true)
 
 // Whether to enable @_used and @_section attributes