bpo-42504: fix for MACOSX_DEPLOYMENT_TARGET=11 (GH-23556)


macOS releases numbering has changed as of macOS 11 Big Sur.  Previously, major releases were of the form 10.x, 10.x+1, 10.x+2, etc; as of Big Sur, they are now x, x+1, etc, so, for example, 10.15, 10.15.1, ..., 10.15.7, 11, 11.0.1, 11.1, ..., 12, 12.1, etc. Allow Python to build with single-digit deployment target values. Patch provided by FX Coudert.
(cherry picked from commit 5291639e611dc3f55a34666036f2c3424648ba50)

Co-authored-by: FX Coudert <fxcoudert@gmail.com>
diff --git a/Lib/distutils/spawn.py b/Lib/distutils/spawn.py
index 0d1bd03..f50edd2 100644
--- a/Lib/distutils/spawn.py
+++ b/Lib/distutils/spawn.py
@@ -54,8 +54,8 @@
         global _cfg_target, _cfg_target_split
         if _cfg_target is None:
             from distutils import sysconfig
-            _cfg_target = sysconfig.get_config_var(
-                                  'MACOSX_DEPLOYMENT_TARGET') or ''
+            _cfg_target = str(sysconfig.get_config_var(
+                                  'MACOSX_DEPLOYMENT_TARGET') or '')
             if _cfg_target:
                 _cfg_target_split = [int(x) for x in _cfg_target.split('.')]
         if _cfg_target:
diff --git a/Lib/distutils/tests/test_build_ext.py b/Lib/distutils/tests/test_build_ext.py
index 5a32e03..1b034c9 100644
--- a/Lib/distutils/tests/test_build_ext.py
+++ b/Lib/distutils/tests/test_build_ext.py
@@ -455,7 +455,7 @@
         deptarget = sysconfig.get_config_var('MACOSX_DEPLOYMENT_TARGET')
         if deptarget:
             # increment the minor version number (i.e. 10.6 -> 10.7)
-            deptarget = [int(x) for x in deptarget.split('.')]
+            deptarget = [int(x) for x in str(deptarget).split('.')]
             deptarget[-1] += 1
             deptarget = '.'.join(str(i) for i in deptarget)
             self._try_compile_deployment_target('<', deptarget)
@@ -488,7 +488,7 @@
 
         # get the deployment target that the interpreter was built with
         target = sysconfig.get_config_var('MACOSX_DEPLOYMENT_TARGET')
-        target = tuple(map(int, target.split('.')[0:2]))
+        target = tuple(map(int, str(target).split('.')[0:2]))
         # format the target value as defined in the Apple
         # Availability Macros.  We can't use the macro names since
         # at least one value we test with will not exist yet.
@@ -497,7 +497,11 @@
             target = '%02d%01d0' % target
         else:
             # for 10.10 and beyond -> "10nn00"
-            target = '%02d%02d00' % target
+            if len(target) >= 2:
+                target = '%02d%02d00' % target
+            else:
+                # 11 and later can have no minor version (11 instead of 11.0)
+                target = '%02d0000' % target
         deptarget_ext = Extension(
             'deptarget',
             [deptarget_c],