Fixed _sys_home computation and added diagnostics for Windows buildbot failures.
diff --git a/Lib/distutils/sysconfig.py b/Lib/distutils/sysconfig.py
index 59315f7..e86cb23 100644
--- a/Lib/distutils/sysconfig.py
+++ b/Lib/distutils/sysconfig.py
@@ -50,6 +50,8 @@
 if _sys_home and os.name == 'nt' and \
     _sys_home.lower().endswith(('pcbuild', 'pcbuild\\amd64')):
     _sys_home = os.path.dirname(_sys_home)
+    if _sys_home.endswith('pcbuild'):   # must be amd64
+        _sys_home = os.path.dirname(_sys_home)
 def _python_build():
     if _sys_home:
         return _is_python_source_dir(_sys_home)