Attempt 3 to fix checkout issues on all package builders
Attempt 3 to fix checkout issues on all package builders

The default architecture for ./tools/test.py was changed from ia32 -> x64, since
we didn't pass it explicitly it was using x64 for testing -- without having it
built first.

(see https://codereview.chromium.org/1408783005)

R=sgjesse@google.com

Review URL: https://chromiumcodereview.appspot.com//1996313002 .

dart-lang/package-bots