test: sandbox: add test for erase command

Add test for the erase command tested on ENV in EXT4.

Signed-off-by: Patrick Delaunay <patrick.delaunay@st.com>
diff --git a/configs/sandbox64_defconfig b/configs/sandbox64_defconfig
index 8a14285..1228c49 100644
--- a/configs/sandbox64_defconfig
+++ b/configs/sandbox64_defconfig
@@ -27,6 +27,7 @@
 # CONFIG_CMD_ELF is not set
 CONFIG_CMD_ASKENV=y
 CONFIG_CMD_GREPENV=y
+CONFIG_CMD_ERASEENV=y
 CONFIG_CMD_ENV_CALLBACK=y
 CONFIG_CMD_ENV_FLAGS=y
 CONFIG_CMD_NVEDIT_EFI=y