This is a br2-external for Zybo Z7-10.
$ cd your/working/dir
$ git clone https://github.com/buildroot/buildroot.git
$ cd buildroot
$ git checkout 2023.08.2
$ make BR2_EXTERNAL=/path/to/this-repo zybo_z7_10_defconfig
$ make
# after build, you can find fw image, output/images/zybo_z7_10.fw
# if you want to configure zybo_z7_10_defconfig, invoke below command
$ make menuconfig
$ sudo fwup output/images/zybo_z7_10.fw