fix #29766, fix #29782 - fix override checker's interface checking

pkg/dev_compiler/tool/build_pkgs.dart

Index: pkg/dev_compiler/tool/build_pkgs.dart
diff --git a/pkg/dev_compiler/tool/build_pkgs.dart b/pkg/dev_compiler/tool/build_pkgs.dart
index 6cad23ee5bcf5596b9903f382fedbf54879ef690..fb60ca4917d160c03d99e2e10f6d3b7af0e92672 100755
--- a/pkg/dev_compiler/tool/build_pkgs.dart
+++ b/pkg/dev_compiler/tool/build_pkgs.dart
@@ -43,7 +43,7 @@ void main(List<String> arguments) {
   }
 
   // Under third_party/pkg.
-  compileModule('collection');
+  compileModule('collection', unsafeForceCompile: true);

[vsm, 2017/07/19 17:19:04]

This will probably break dartdevc snapshot generation too.  The snapshot is
built by compiling ddc against itself.  Looks like we import package:collection.

Can you land your fix there and roll it forward?  To roll forward, update this
to new tag or hash:

https://github.com/dart-lang/sdk/blob/master/DEPS#L61

[Jennifer Messerly, 2017/07/20 19:15:50]

done

   compileModule('matcher');
   compileModule('path');
   if (isTravis) {