MSYS: Force relpath and outpath into same pathing namespace.

MSYS bash (and other msys-compiled executables) perform path
transformation much like Cygwin. This causes syncqt path
substitution to not work correctly, so use 'pwd -W' to get
the Windows version (though with forward slashes) of both
relpath and outpath.

Change-Id: I808e3ef9206ed5f5bd8b6879d12afe664e589e0c
Reviewed-by: Alvaro Burnett <alvaroburnett@gmail.com>
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@digia.com>

configure

@@ -446,6 +446,8 @@ if [ "$OSTYPE" = "msys" ]; then
     BUILD_ON_MSYS=yes
     DEV_NULL=/tmp/empty-file
     echo "" > $DEV_NULL
+    relpath=`(cd "$relpath"; pwd -W)`
+    outpath=`pwd -W`
 fi
 
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