Skip buildx test with VFS podman storage driver

Ref: https://github.com/containers/podman/issues/17520

Signed-off-by: Chris Evich <cevich@redhat.com>

test/system/070-build.bats

@@ -30,6 +30,11 @@ EOF
 }
 
 @test "podman buildx - basic test" {
+    run_podman info --format "{{.Store.GraphDriverName}}"
+    if [[ "$output" == "vfs" ]]; then
+        skip "Test not supported with VFS podman storage driver (#17520)"
+    fi
+
     rand_filename=$(random_string 20)
     rand_content=$(random_string 50)