Fix build for macOS 11 SDK am: 6a4b58d73d am: 8c5e412865 am: a6ecdfa003 am: 369499f7b9

Original change: https://android-review.googlesource.com/c/platform/external/python/cpython2/+/1362702

Change-Id: Ic452ba0d7ced553f29be56b4aa146c409a675c20
diff --git a/Modules/getpath.c b/Modules/getpath.c
index 27f3381..181354d 100644
--- a/Modules/getpath.c
+++ b/Modules/getpath.c
@@ -7,6 +7,7 @@
 #include <string.h>
 
 #ifdef __APPLE__
+#include <AvailabilityMacros.h>
 #include <mach-o/dyld.h>
 #endif