t3300: skip when filesystem does not like TAB in filenames.

Instead of checking Cygwin explicitly, see if the filesystem lets us
create funny filenames.

Signed-off-by: Junio C Hamano <junkio@cox.net>

t/t3300-funny-names.sh

@@ -9,9 +9,6 @@ This test tries pathnames with funny characters in the working
 tree, index, and tree objects.
 '
 
-# since FAT/NTFS does not allow tabs in filenames, skip this test
-test "$(uname -o 2>/dev/null)" = Cygwin && exit 0
-
 . ./test-lib.sh
 
 p0='no-funny'
@@ -27,6 +24,12 @@ EOF
 cat >"$p1" "$p0"
 echo 'Foo Bar Baz' >"$p2"
 
+test -f "$p1" && cmp "$p0" "$p1" || {
+	# since FAT/NTFS does not allow tabs in filenames, skip this test
+	say 'Your filesystem does not allow tabs in filenames, test skipped.'
+	test_done
+}
+
 echo 'just space
 no-funny' >expected
 test_expect_success 'git-ls-files no-funny' \