relaxed test, ignoring case of drive letter.

Thanks to Mat Marcus for the fix.

[SVN r44551]

tools/build

@@ -1 +1 @@
-Subproject commit 11a57cc02124091a3777d885f8fc6883993b848b
+Subproject commit 3975f3105a646a6edd0d286b52123f6d44476bb4