t9200: On MSYS, do not pass Windows-style paths to CVS

For details, see the commit message of 4114156ae9. Note that while using
$PWD as part of GIT_DIR is not required here, it does no harm and it is
more consistent. In addition, on MSYS using an environment variable should
be slightly faster than spawning an external executable.

Signed-off-by: Sebastian Schuberth <sschuberth@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t9200-git-cvsexportcommit.sh

@@ -19,9 +19,9 @@ then
     test_done
 fi
 
-CVSROOT=$(pwd)/cvsroot
-CVSWORK=$(pwd)/cvswork
-GIT_DIR=$(pwd)/.git
+CVSROOT=$PWD/cvsroot
+CVSWORK=$PWD/cvswork
+GIT_DIR=$PWD/.git
 export CVSROOT CVSWORK GIT_DIR
 
 rm -rf "$CVSROOT" "$CVSWORK"