Remove runtest dependency on current dir being build top.

This change is necessary to support relative path based args.
diff --git a/testrunner/runtest.py b/testrunner/runtest.py
index e637b71..b6938cd 100755
--- a/testrunner/runtest.py
+++ b/testrunner/runtest.py
@@ -221,7 +221,10 @@
               self._options.make_jobs)
         logger.Log(cmd)
         if not self._options.preview:
+          old_dir = os.getcwd()
+          os.chdir(self._root_path)
           run_command.RunCommand(cmd, return_output=False)
+          os.chdir(old_dir)
       target_build_string = " ".join(list(target_set))
       extra_args_string = " ".join(list(extra_args_set))
       # mmm cannot be used from python, so perform a similar operation using
@@ -253,6 +256,8 @@
       if os.path.isfile(os.path.join(self._root_path, build_file_path)):
         target_set.add(build_file_path)
         return True
+      else:
+        logger.Log("%s has no Android.mk, skipping" % build_dir)
     return False
 
   def _GetTestsToRun(self):
diff --git a/testrunner/test_defs/native_test.py b/testrunner/test_defs/native_test.py
index ad7352a..e6917c9 100644
--- a/testrunner/test_defs/native_test.py
+++ b/testrunner/test_defs/native_test.py
@@ -52,7 +52,7 @@
     # find all test files, convert unicode names to ascii, take the basename
     # and drop the .cc/.cpp  extension.
     source_list = []
-    build_path = self.GetBuildPath()
+    build_path = os.path.join(android_build.GetTop(), self.GetBuildPath())
     os.path.walk(build_path, self._CollectTestSources, source_list)
     logger.SilentLog("Tests source %s" % source_list)