Allow test.dart dartc/junit_tests to be run from the compiler subdirectory.
Allow test.dart dartc/junit_tests to be run from the compiler subdirectory.

BUG=
TEST=cd compiler; ../tools/build.py dartc; ../tools/test.dart -cdartc dartc/junit_tests

Review URL: http://codereview.chromium.org//9188032

git-svn-id: c93d8a2297af3b929165606efe145742a534bc71@3237 260f80e4-7a28-3924-810f-c04153c831b5

dartino/dart-sdk,dart-archive/dart-sdk,dart-archive/dart-sdk,dart-archive/dart-sdk,dart-lang/sdk,dart-archive/dart-sdk,dart-lang/sdk,dart-lang/sdk,dart-archive/dart-sdk,dart-archive/dart-sdk,dart-archive/dart-sdk,dartino/dart-sdk,dartino/dart-sdk,dart-archive/dart-sdk,dartino/dart-sdk,dartino/dart-sdk,dart-lang/sdk,dartino/dart-sdk,dart-lang/sdk,dartino/dart-sdk,dart-lang/sdk,dart-lang/sdk,dartino/dart-sdk,dartino/dart-sdk,dart-lang/sdk,dart-archive/dart-sdk