meson: do the macos sdk version comparison in meson

Since we can no longer rely on distuils for a version comparison, let's
modify the macos-sdk-version script so it returns multiple potential
versions to meson. Then use meson's built-in version comparison to pick
the right one instead. This avoids the complication of needing certain
python packages installed since everything simply uses stdlib functions.

meson.build

@@ -1477,7 +1477,9 @@ macos_sdk_version = '0.0'
 if darwin and macos_sdk_version_py.found()
     macos_sdk_info = run_command(macos_sdk_version_py, check: true).stdout().split(',')
     macos_sdk_path = macos_sdk_info[0].strip()
-    macos_sdk_version = macos_sdk_info[1]
+    # Always pick whichever version is higher.
+    macos_sdk_version = macos_sdk_info[1].version_compare('>' + macos_sdk_info[2]) ? \
+                        macos_sdk_info[1] : macos_sdk_info[2]
 endif
 
 if macos_sdk_path != ''