Only do CF version test on r8lib when testing r8lib.

Change-Id: I9e2843ca90e0ecb74c0b1d5b24084bc3d97efd97
diff --git a/src/test/java/com/android/tools/r8/R8CfVersionTest.java b/src/test/java/com/android/tools/r8/R8CfVersionTest.java
index 8e9b11c..fcc29c1 100644
--- a/src/test/java/com/android/tools/r8/R8CfVersionTest.java
+++ b/src/test/java/com/android/tools/r8/R8CfVersionTest.java
@@ -5,6 +5,7 @@
 package com.android.tools.r8;
 
 import static org.junit.Assert.assertTrue;
+import static org.junit.Assume.assumeTrue;
 
 import com.android.tools.r8.cf.CfVersion;
 import com.android.tools.r8.utils.codeinspector.CodeInspector;
@@ -43,6 +44,8 @@
 
   @Test
   public void testCfVersionR8Lib() throws IOException {
+    // Only run when testing R8 lib as only then do we know it is built and up-to-date.
+    assumeTrue(ToolHelper.isTestingR8Lib());
     CodeInspector inspector = new CodeInspector(ToolHelper.R8LIB_JAR);
     inspector.forAllClasses(
         clazz -> {