--- a
+++ b/config/cmake/Modules/CheckPrototypeExists.cxx.in
@@ -0,0 +1,13 @@
+#include <${FILE}>
+
+${CHECK_PROTOTYPE_EXISTS_CXX_EXTERNC_BEGIN}
+
+typedef union { int member; } dummyStruct;
+
+dummyStruct ${FUNC}( dummyStruct );
+
+${CHECK_PROTOTYPE_EXISTS_CXX_EXTERNC_END}
+
+int main() {
+  return 0;
+}