include pgrx-cshim-static.cpp if bindgen thinks there are cppflags

Author: usamoi

pgrx-pg-sys/pgrx-cshim.c

@@ -8,7 +8,13 @@
 //LICENSE
 //LICENSE Use of this source code is governed by the MIT license that can be found in the LICENSE file.
 
-#include "pgrx-cshim-static.c"
+#if __has_include("pgrx-cshim-static.c")
+    #include "pgrx-cshim-static.c"
+#endif
+
+#if __has_include("pgrx-cshim-static.cpp")
+    #include "pgrx-cshim-static.cpp"
+#endif
 
 void SpinLockInit__pgrx_cshim(volatile slock_t *lock) {
     SpinLockInit(lock);