BLD: fix build error for PyPy (pandas-dev#26536)

Author: robbuckley

setup.py

@@ -11,7 +11,7 @@
 
 import pkg_resources
 import platform
-from distutils.sysconfig import get_config_var
+from distutils.sysconfig import get_config_vars
 import sys
 import shutil
 from distutils.version import LooseVersion
@@ -442,19 +442,18 @@ def run(self):
     if debugging_symbols_requested:
         extra_compile_args.append('-g')
 
-# For mac, ensure extensions are built for macos 10.9 when compiling on a
-# 10.9 system or above, overriding distuitls behaviour which is to target
-# the version that python was built for. This may be overridden by setting
-# MACOSX_DEPLOYMENT_TARGET before calling setup.py
+# For mac, ensure extensions are built for at least macOS 10.9 when compiling
+# on a 10.9 system or above, overriding CPython distuitls behaviour which is
+# to target the version that python was built for. This may be overridden by
+# setting MACOSX_DEPLOYMENT_TARGET before calling setup.py
 if is_platform_mac():
     if 'MACOSX_DEPLOYMENT_TARGET' not in os.environ:
         current_system = LooseVersion(platform.mac_ver()[0])
         python_target = LooseVersion(
-            get_config_var('MACOSX_DEPLOYMENT_TARGET'))
+            get_config_vars().get('MACOSX_DEPLOYMENT_TARGET', current_system))
         if python_target < '10.9' and current_system >= '10.9':
             os.environ['MACOSX_DEPLOYMENT_TARGET'] = '10.9'
 
-
 # enable coverage by building cython files by setting the environment variable
 # "PANDAS_CYTHON_COVERAGE" (with a Truthy value) or by running build_ext
 # with `--with-cython-coverage`enabled