t5547-push-quarantine: run the path separator test on Windows, too

t5547-push-quarantine: run the path separator test on Windows, too

To perform the test case on Windows in a way that corresponds to the
POSIX version, inject the semicolon in a directory name.

Typically, an absolute POSIX style path, such as the one in $PWD, is
translated into a Windows style path by bash when it invokes git.exe.
However, the presence of the semicolon suppresses this translation;
but the untranslated POSIX style path is useless for git.exe.
Therefore, instead of $PWD pass the Windows style path that $(pwd)
produces.

Signed-off-by: Johannes Sixt <j6t@kdbg.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>