Add stub GDEF files
diff --git a/src/harfbuzz-private.h b/src/harfbuzz-private.h
new file mode 100644
index 0000000..4d3eb69
--- /dev/null
+++ b/src/harfbuzz-private.h
@@ -0,0 +1,6 @@
+#ifndef HARFBUZZ_PRIVATE_H
+#define HARFBUZZ_PRIVATE_H
+
+#include <assert.h>
+
+#endif /* HARFBUZZ_PRIVATE_H */