Exclude 'test' and 'testcases' from lib/ packages.

R=paulberry@google.com, whesse@google.com
BUG= https://github.com/dart-lang/sdk/issues/29852

Review-Url: https://codereview.chromium.org/2940723002 .
diff --git a/sdk/BUILD.gn b/sdk/BUILD.gn
index 51c44d0..116f721 100644
--- a/sdk/BUILD.gn
+++ b/sdk/BUILD.gn
@@ -385,7 +385,7 @@
     visibility = [ ":copy_analyzer_sources" ]
     source = "../pkg/$analyzer_source_dir"
     dest = "$root_out_dir/dart-sdk/lib/$analyzer_source_dir"
-    exclude = "*.svn,doc,*.py,*.gypi,*.sh,.gitignore,packages"
+    exclude = "*.svn,doc,*.py,*.gypi,*.sh,.gitignore,packages,test,testcases"
   }
 }