Bug 41995: Generated headers on Windows are not reproducible

The flags optionally passed as a third parameter to DLL_BLOCKLIST_ENTRY
are stored in a set, so they are not ordered.
Sorting them before outputting them makes the creation of the headers
deterministic.

toolkit/xre/dllservices/mozglue/gen_dll_blocklist_defs.py

@@ -570,7 +570,7 @@ class DllBlocklistEntry(object):
 
         flags_str = ""
 
-        flags = self.get_flags_list()
+        flags = sorted(self.get_flags_list())
         if flags:
             flags_str = ", " + " | ".join(map(self.get_flag_string, flags))