Correct inconsistency from pwd in root directory

When running pwd -W while on /, it will display the windows path with a
trailing slash. In all other cases it omits the trailing slash. This
patch corrects this error when setting the root variable for the
0005-mangle.mingw.patch for the file check-sysroot.
Merge branch 'master' of github.com:daramarak/MINGW-packages