Search packages/non-core/*/packages for local packages.

Currently this finds only Blaze-related packages, but it does so without
hard-coding "blaze" in tools code.

tools/project-context.js

@@ -607,7 +607,13 @@ _.extend(ProjectContext.prototype, {
     if (! self._ignoreCheckoutPackages && files.inCheckout()) {
       // Running from a checkout, so use the Meteor core packages from the
       // checkout.
-      searchDirs.push(files.pathJoin(files.getCurrentToolsDir(), 'packages'));
+      const packagesDir =
+        files.pathJoin(files.getCurrentToolsDir(), 'packages');
+
+      searchDirs.push(
+        packagesDir,
+        files.pathJoin(packagesDir, "non-core", "*", "packages"),
+      );
     }
     return searchDirs;
   },

tools/tool-env/isopackets.js

@@ -221,6 +221,9 @@ var newIsopacketBuildingCatalog = function () {
   var messages = buildmessage.capture(
     { title: "scanning local core packages" },
     function () {
+      const packagesDir =
+        files.pathJoin(files.getCurrentToolsDir(), 'packages');
+
       // When running from a checkout, isopacket building does use local
       // packages, but *ONLY THOSE FROM THE CHECKOUT*: not app packages or
       // $PACKAGE_DIRS packages.  One side effect of this: we really really
@@ -228,7 +231,8 @@ var newIsopacketBuildingCatalog = function () {
       // (there's no worries about needing to springboard).
       isopacketCatalog.initialize({
         localPackageSearchDirs: [
-          files.pathJoin(files.getCurrentToolsDir(), 'packages'),
+          packagesDir,
+          files.pathJoin(packagesDir, "non-core", "*", "packages"),
         ],
         buildingIsopackets: true
       });