t5000: skip ZIP tests if unzip was not found

Signed-off-by: Johannes Schindelin <Johannes.Schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t5000-tar-tree.sh

@@ -108,6 +108,13 @@ test_expect_success \
     'git-archive --format=zip' \
     'git-archive --format=zip HEAD >d.zip'
 
+$UNZIP -v 2>/dev/null
+if [ $? -eq 127 ]; then
+	echo "Skipping ZIP tests, because unzip was not found"
+	test_done
+	exit
+fi
+
 test_expect_success \
     'extract ZIP archive' \
     '(mkdir d && cd d && $UNZIP ../d.zip)'