Make python3 build on macOS 11, including for arm64

There is no /usr/lib/libz.dylib any longer in macOS 11.

No idea whether it works (especially on arm64), but that is another
issue.

Change-Id: I92ac0c500388730eca0be4766f07b1af2d2808e0
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/105897
Tested-by: Jenkins
Reviewed-by: Tor Lillqvist <tml@collabora.com>

external/python3/UnpackedTarball_python3.mk

@@ -23,6 +23,7 @@ $(eval $(call gb_UnpackedTarball_add_patches,python3,\
 	external/python3/ubsan.patch.0 \
 	external/python3/python-3.5.tweak.strip.soabi.patch \
 	external/python3/darwin.patch.0 \
+	external/python3/macos-11.patch.0 \
 ))
 
 ifneq ($(filter DRAGONFLY FREEBSD LINUX NETBSD OPENBSD SOLARIS,$(OS)),)

external/python3/macos-11.patch.0

@@ -0,0 +1,38 @@
+-*- Mode: diff -*-
+--- configure
++++ configure
+@@ -9372,6 +9275,9 @@
+     	esac
+     else
+     	case `/usr/bin/arch` in
++     	arm64)
++    		MACOSX_DEFAULT_ARCH="arm64"
++     		;;
+     	i386)
+     		MACOSX_DEFAULT_ARCH="x86_64"
+     		;;
+--- Mac/Tools/pythonw.c
++++ Mac/Tools/pythonw.c
+@@ -121,6 +121,8 @@
+     cpu_types[0] = CPU_TYPE_POWERPC;
+ #elif defined(__i386__)
+     cpu_types[0] = CPU_TYPE_X86;
++#elif defined(__arm64__)
++    cpu_types[0] = CPU_TYPE_ARM64;
+ #else
+ #       error "Unknown CPU"
+ #endif
+--- setup.py
++++ setup.py
+@@ -670,7 +670,10 @@
+             add_dir_to_list(self.compiler.include_dirs,
+                             sysconfig.get_config_var("INCLUDEDIR"))
+ 
+-        system_lib_dirs = ['/lib64', '/usr/lib64', '/lib', '/usr/lib']
++        if MACOS:
++            system_lib_dirs = ['/usr/lib', macosx_sdk_root()+'/usr/lib']
++        else:
++            system_lib_dirs = ['/lib64', '/usr/lib64', '/lib', '/usr/lib']
+         system_include_dirs = ['/usr/include']
+         # lib_dirs and inc_dirs are used to search for files;
+         # if a file is found in one of those directories, it can