test: hush: Test hush variable expansion

Verifies shell variables are replaced by their values.

Reviewed-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Francis Laniel <francis.laniel@amarulasolutions.com>
diff --git a/test/hush/Makefile b/test/hush/Makefile
index a3c9ae5..feb4f71 100644
--- a/test/hush/Makefile
+++ b/test/hush/Makefile
@@ -5,3 +5,4 @@
 
 obj-y += cmd_ut_hush.o
 obj-y += if.o
+obj-y += dollar.o