config: sandbox: Add unit tests

Add unit tests for sandbox default config.

Signed-off-by: Pantelis Antoniou <pantelis.antoniou@konsulko.com>
Acked-by: Simon Glass <sjg@chromium.org>
diff --git a/configs/sandbox_defconfig b/configs/sandbox_defconfig
index 4c4e480..54120c2 100644
--- a/configs/sandbox_defconfig
+++ b/configs/sandbox_defconfig
@@ -189,7 +189,9 @@
 CONFIG_TPM=y
 CONFIG_LZ4=y
 CONFIG_ERRNO_STR=y
+CONFIG_OF_LIBFDT_OVERLAY=y
 CONFIG_UNIT_TEST=y
 CONFIG_UT_TIME=y
 CONFIG_UT_DM=y
 CONFIG_UT_ENV=y
+CONFIG_UT_OVERLAY=y