[lit] Actually do normalize the case of files in the config map.

[lit] Actually do normalize the case of files in the config map.

This has gone back and forth, but it seems this is necessary
after all.  realpath is not sufficient because if you have a
file named 'C:\foo.txt', then both realpath('c:\foo.txt') and
realpath(C:\foo.txt') return the string that was passed to them
exactly as is, meaning the case of the drive-letter won't match.

The problem before was not that we were normalizing the case of
items going into the config map, but rather that we were
normalizing the case of something we needed to print.  The value
that is used to key on the config map should never be printed.

llvm-svn: 313918