Run gradle clean on internal bots

We have leftover jctf tests in the build directory when we switch from
old branches

Change-Id: I7275b544be3f65ef7944ad527f44f80fca886b27
diff --git a/tools/internal_test.py b/tools/internal_test.py
index df4174f..8e4caa5 100755
--- a/tools/internal_test.py
+++ b/tools/internal_test.py
@@ -111,6 +111,8 @@
 
 # TODO(b/210982978): Enable testing of min xmx again
 TEST_COMMANDS = [
+    # Make sure we have a clean build to not be polluted by old test files
+    ['tools/gradle.py', 'clean'],
     # Run test.py internal testing.
     ['tools/test.py', '--only_internal', '--slow_tests',
      '--java_max_memory_size=8G'],