tests: fix path separator, use g_build_filename()

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Message-Id: <20230306122751.2355515-2-marcandre.lureau@redhat.com>
diff --git a/tests/unit/test-io-channel-command.c b/tests/unit/test-io-channel-command.c
index c6e66a8..4f02261 100644
--- a/tests/unit/test-io-channel-command.c
+++ b/tests/unit/test-io-channel-command.c
@@ -35,7 +35,7 @@
 static void test_io_channel_command_fifo(bool async)
 {
     g_autofree gchar *tmpdir = g_dir_make_tmp("qemu-test-io-channel.XXXXXX", NULL);
-    g_autofree gchar *fifo = g_strdup_printf("%s/%s", tmpdir, TEST_FIFO);
+    g_autofree gchar *fifo = g_build_filename(tmpdir, TEST_FIFO, NULL);
     g_autofree gchar *srcargs = g_strdup_printf("%s - PIPE:%s,wronly", socat, fifo);
     g_autofree gchar *dstargs = g_strdup_printf("%s PIPE:%s,rdonly -", socat, fifo);
     g_auto(GStrv) srcargv = g_strsplit(srcargs, " ", -1);