t4210: skip command-line encoding tests on mingw
t4210: skip command-line encoding tests on mingw

On Windows the application command line is provided as unicode and in
mingw-git we convert that to utf-8. So these tests that require a iso-8859-1
input are being subverted by the encoding transformations we perform and
should be skipped.

Signed-off-by: Pat Thoyts <fe43a83262eef1680511f524a1e74d43c633cffe@users.sourceforge.net>
Signed-off-by: Stepan Kasal <257b363030caa50dbc1cdef9b268d9d56bf639f1@ucw.cz>
Signed-off-by: Junio C Hamano <a6723cc3f76163bf7adb636a73ac3b0ceb3e6b9b@pobox.com>

destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git