test: cmd: add test for spawn and wait commands

Test the spawn and wait commands.

Signed-off-by: Jerome Forissier <jerome.forissier@linaro.org>
Acked-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
diff --git a/test/cmd/Makefile b/test/cmd/Makefile
index 8596c5a..595e4cf 100644
--- a/test/cmd/Makefile
+++ b/test/cmd/Makefile
@@ -39,3 +39,4 @@
 endif
 obj-$(CONFIG_ARM_FFA_TRANSPORT) += armffa.o
 endif
+obj-$(CONFIG_CMD_SPAWN) += spawn.o