Open-source MockCcSupport and some tests for LibraryLinkingTest.

Also changed the setup of BazelAnalysisMock.

--
MOS_MIGRATED_REVID=109890009
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 b6d3e54..a2c073b 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
@@ -69,5 +69,5 @@
 
   public static final String TOOLS_REPOSITORY = "@bazel_tools";
 
-  public static final String MOCK_CROSSTOOL_PATH = "tools/cpp";
+  public static final String TOOLS_REPOSITORY_PATH = "tools/cpp";
 }