sandbox: Enable some ENV commands

Enable some additional ENV commands in sandbox to aid in build testing
and run testing.

Signed-off-by: Joe Hershberger <joe.hershberger@ni.com>
Reviewed-by: Simon Glass <sjg@chromium.org>

include/configs/sandbox.h

@@ -153,6 +153,11 @@
 
 #define CONFIG_CMD_SANDBOX
 
+#define CONFIG_CMD_ENV_FLAGS
+#define CONFIG_CMD_ENV_CALLBACK
+#define CONFIG_CMD_GREPENV
+#define CONFIG_CMD_ASKENV
+
 #define CONFIG_BOOTARGS ""
 
 #define CONFIG_BOARD_LATE_INIT