On Windows, use lowercased file suffix when determining the file

target.

Suggested by John Reid.


[SVN r49697]

tools/build

@@ -1 +1 @@
-Subproject commit 6d3911e870795416f4cc44073d526d648f52a8fc
+Subproject commit bb8c997c17a73202d2f6f83ec04863202b1b35e1