Closes #15367: Corrected computation of include locations for source builds on…

Closes #15367: Corrected computation of include locations for source builds on Windows. Thanks to Richard Oudkerk for the bug report and patch.

Lib/distutils/command/build_ext.py

@@ -8,6 +8,7 @@ import sys, os, re
 from distutils.core import Command
 from distutils.errors import *
 from distutils.sysconfig import customize_compiler, get_python_version
+from distutils.sysconfig import get_config_h_filename
 from distutils.dep_util import newer_group
 from distutils.extension import Extension
 from distutils.util import get_platform
@@ -196,7 +197,10 @@ class build_ext(Command):
 
             # Append the source distribution include and library directories,
             # this allows distutils on windows to work in the source tree
-            self.include_dirs.append(os.path.join(sys.exec_prefix, 'PC'))
+            self.include_dirs.append(os.path.dirname(get_config_h_filename()))
+            _sys_home = getattr(sys, '_home', None)
+            if _sys_home:
+                self.library_dirs.append(_sys_home)
             if MSVC_VERSION >= 9:
                 # Use the .lib files for the correct architecture
                 if self.plat_name == 'win32':