Keep tooltool manifests in sync (port bug 1369115: Update win64 builders to rust 1.18.0-beta.4). rs=bustage-fix

mail/config/tooltool-manifests/win64/releng.manifest

@@ -6,9 +6,9 @@
     "filename": "mozmake.exe"
   },
   {
-    "version": "rustc 1.17.0 (56124baa9 2017-04-24) repack with cargo 0.19.0-beta.1 (03efb7fc8 2017-04-23)",
-    "size": 83368214,
-    "digest": "2f1dda29e495e9707a0e22cde5c80525bd202be9a3381dd053edf08e1a54cd7fa4106e8f1cec336daaae62252ef02cf5b76079c0495a90f1ac0b823a16fd27dc",
+    "version": "1.18.0-beta.4 (0308c9865 2017-05-27)",
+    "size": 98338423,
+    "digest": "126dd7054f4d2a705e3abf0f916b62904ae5097b70f67c9d048e031e42a19208c41885c0d479a6f3591f2c74725c4e80ed3dfa4452301618cc7ac0f0820d5683",
     "algorithm": "sha512",
     "visibility": "public",
     "filename": "rustc.tar.bz2",