bpo-45220: Ensure RT_MANIFEST is defined when compiling Windows resource files (pythonGH-29501)

Author: thatbirdguythatuknownot

PC/python_exe.rc

@@ -2,6 +2,12 @@
 
 #include "python_ver_rc.h"
 
+#ifndef RT_MANIFEST
+// bpo-45220: Cannot reliably #include RT_MANIFEST from
+// anywhere, so we hardcode it
+#define RT_MANIFEST 24
+#endif
+
 // Include the manifest file that indicates we support all
 // current versions of Windows.
 1 RT_MANIFEST "python.manifest"