I can not build u-boot-fw-utils , and can I use fw_printenv, fw_setenv in user space to set uboot environment variables on maaxboard?

[gitgonewithwind]

Hi all
I am playing rauc. there are two rootfs to boot.
so need to change uboot environment variables to switch boot between the first rootfs and redundant rootfs.
so need to add IMAGE_INSTALL_append +="u-boot-fw-utils " in yocto local file to enable fw_printenv, fw_setenv.
but bitbake can not pass build u-boot-fw-utils. it shows can find maaxboard_defconfig. so I use imx8mq_evk_defconfig to instead it.
it can pass building. but after bootup, I run fw_printenv , it shows error : can not find /dev/mtd1. and can not find /dev/mtd either
before I did not add IMAGE_INSTALL_append +="u-boot-fw-utils " , of course, there was not command fw_printenv. but it could find /dev/mtd ,only no content.

My question is that I want to know do I can use fw_printenv ? or Can I use uEnv.txt to change uboot environment variables to switch boot the two rootfs' ?
any help?
Thank you