Use Wincent Icon Utility for setting custom folder icons (buildtools, 9abc011)

The most recent update to the Xcode Tools breaks the previously existing mechanism for applying custom icons to folders.

I've developed a custom Foundation/Carbon tool to replace the old procedure; this commit switches over buildtools to use the new tool. I will document the new dependency in another commit.

Signed-off-by: Greg Hurrell <greg@hurrell.net>