versioner: compile headers in both C and C++ mode.

Bug: https://github.com/android-ndk/ndk/issues/440
Test: python run_tests.py
Change-Id: Ib572a8fdcc00f6b88a25003a085b16ce9698d692
diff --git a/tools/versioner/tests/extern_cpp/run.sh b/tools/versioner/tests/extern_cpp/run.sh
new file mode 100644
index 0000000..e320c95
--- /dev/null
+++ b/tools/versioner/tests/extern_cpp/run.sh
@@ -0,0 +1 @@
+versioner headers -p platforms -r arm -a 21 -a 23 -i