Index: llvm/trunk/test/Unit/lit.cfg
===================================================================
--- llvm/trunk/test/Unit/lit.cfg
+++ llvm/trunk/test/Unit/lit.cfg
@@ -43,6 +43,10 @@
     config.environment['PATH'] = os.path.pathsep.join((
             config.shlibdir, config.environment['PATH']))
 
+# Win32 may use %SYSTEMDRIVE% during file system shell operations, so propogate.
+if sys.platform == 'win32' and 'SYSTEMDRIVE' in os.environ:
+    config.environment['SYSTEMDRIVE'] = os.environ['SYSTEMDRIVE']
+
 ###
 
 # Check that the object root is known.