Use fixed mx version

Author: gilles-duboscq

ci.jsonnet

@@ -7,7 +7,7 @@ local defs = import 'defs.jsonnet';
   // Used to run fewer jobs
   local debug = false,
 
-  local overlay = '589714435d27cd69293fe42a8f75ecdd76bd1d06',
+  local overlay = '55445982aa4ce8431ee557ba5becc515ab9544f8',
 
   local no_overlay = 'cb733e564850cd37b685fcef6f3c16b59802b22c',
 

common.jsonnet

@@ -40,6 +40,7 @@ local common_json = (import "common.json");
 
   local common = python3 + {
     packages+: {
+      'mx': '5.317.1',
       'pip:pylint': '==1.9.3',
       'pip:ninja_syntax': '==1.7.2',
     },