Pass NDK path to test_libcxx.py.

If we gave the test runner an alternate NDK under test, it would
still run the libc++ tests against the default one because we weren't
passing along the NDK path.

Test: ./run_tests.py --suite libc++ --abi armeabi-v7a /path/to/r14
Bug: None
Change-Id: I9dca2f2b3899cb412cb1f5c9d28d8f116e22a969
diff --git a/tests/testlib.py b/tests/testlib.py
index ee713bf..7a1b02e 100644
--- a/tests/testlib.py
+++ b/tests/testlib.py
@@ -1308,6 +1308,9 @@
             'python', '../test_libcxx.py',
             '--abi', self.abi,
             '--platform', str(self.api),
+            '--xunit-xml-output=' + xunit_output,
+            '--timeout=600',
+            '--ndk=' + os.environ['NDK'],
 
             # We don't want the progress bar since we're already printing our
             # own output, so we need --show-all so we get *some* output,
@@ -1315,10 +1318,6 @@
             # wouldn't be clear if something had hung.
             '--no-progress-bar',
             '--show-all',
-
-            '--xunit-xml-output=' + xunit_output,
-
-            '--timeout=600',
         ]
 
         if self.deprecated_headers: