"meteor rebuild-all" should not try to rebuild warehouse packages.

That's because warehouse packages are now pre-built and have no source tree.

(The existing code didn't work anyway. It iterated over self.releaseManifest
instead of self.releaseManifest.packages, and the "name" and "version" arguments
to the each were reversed. So it was trying to delete directories named ".build"
inside "/Users/glasser/.meteor/packages/de0d7206ad/tools" and
"/Users/glasser/.meteor/packages/packages". Since those directories never
existed, it didn't manage to try to rebuild any packages anyway.)