AArch64 / macOS: use __DATA,__CONST section instead of .const (temporary fix)

The .const section cannot contain absolute references to symbols,
as these may need relocation and therefore must be writable.
This should be fixed more generally by distinguishing between initialization
data that contains absolute references to symbols and initialization data
that does not.

aarch64/TargetPrinter.ml

@@ -226,7 +226,7 @@ module MacOS_System : SYSTEM =
       | Section_data i | Section_small_data i ->
           if i || (not !Clflags.option_fcommon) then ".data" else "COMM"
       | Section_const i  | Section_small_const i ->
-          if i || (not !Clflags.option_fcommon) then ".const" else "COMM"
+          if i || (not !Clflags.option_fcommon) then ".section	__DATA,__CONST" else "COMM"
       | Section_string -> ".const"
       | Section_literal -> ".const"
       | Section_jumptable -> ".text"