Perform build and magnum tuning

Building o//third_party/python now takes 5 seconds on my PC

This change works towards modifying Python to use runtime dispatching
when appropriate. For example, when loading the magnums in the socket
module, it's a good idea to check if the magnum is zero, because that
means the local system platform doesn't support it.

third_party/python/Python/dynload_shlib.c

@@ -1,24 +1,7 @@
-
-/* Support for dynamic loading of extension modules */
-
-#include "Python.h"
-#include "importdl.h"
-
-#include <sys/types.h>
-#include <sys/stat.h>
-
-#if defined(__NetBSD__)
-#include <sys/param.h>
-#if (NetBSD < 199712)
-#include <nlist.h>
-#include <link.h>
-#define dlerror() "error in dynamic linking"
-#endif
-#endif /* NetBSD */
-
-#ifdef HAVE_DLFCN_H
 #include "libc/runtime/dlfcn.h"
-#endif
+#include "third_party/python/Include/Python.h"
+#include "third_party/python/Python/importdl.h"
+/* clang-format off */
 
 #if (defined(__OpenBSD__) || defined(__NetBSD__)) && !defined(__ELF__)
 #define LEAD_UNDERSCORE "_"