Rollback of commit 82d43279f93d95e4c41b4bc598a3cc05ddd1ae1a.

*** Reason for rollback ***

Breaks TensorFlow and other Bazel jobs on ci.bazel.io

*** Original change description ***

Change execution root for external repositories to be ../repo

Some of the important aspect of this change:

* Remote repos in the execution root are under output_base/execroot/repo_name, so the prefix is ../repo_name (to escape the local workspace name).
* Package roots for external repos were previously "output_base/", they are now output_base/external/repo_name (which means source artifacts always have a relative path from their repository).
* Outputs are under bazel-bin/external/repo_name/ (or similarly under genfiles). Note that this is a bit of a change from how this was implemented in the previous cl.

Fixes #1262.

RELNOTES[INC]: Previously, an external repository would be symlinked into the
execution root at execroot/local_repo/external/remote_repo. This changes it to
be at execroot/remote_repo. This may break genrules/Skylark actions that
hardcode execution root paths. If this causes breakages for you, ensure that
genrules are using $(location :target) to access files and Skylark rules are
using http://bazel.io/docs/skylark/lib/File.html's path, dirname, etc.
functions.

Roll forward of bdfd58a.

--
MOS_MIGRATED_REVID=133709658
diff --git a/src/test/java/com/google/devtools/build/lib/testutil/TestConstants.java b/src/test/java/com/google/devtools/build/lib/testutil/TestConstants.java
index ba50706..8db1105 100644
--- a/src/test/java/com/google/devtools/build/lib/testutil/TestConstants.java
+++ b/src/test/java/com/google/devtools/build/lib/testutil/TestConstants.java
@@ -65,7 +65,7 @@
         "com.google.devtools.build.lib.bazel.rules.BazelRulesModule";
   public static final ImmutableList<String> IGNORED_MESSAGE_PREFIXES = ImmutableList.<String>of();
 
-  public static final String GCC_INCLUDE_PATH = "../bazel_tools/tools/cpp/gcc3";
+  public static final String GCC_INCLUDE_PATH = "external/bazel_tools/tools/cpp/gcc3";
 
   public static final String TOOLS_REPOSITORY = "@bazel_tools";