reproduce (this is a W=1 build):
        # https://github.com/Xilinx/linux-xlnx/commit/116fbf86655bcc669b416defceabf085291f4500
        git remote add xilinx-xlnx https://github.com/Xilinx/linux-xlnx
        git fetch --no-tags xilinx-xlnx xlnx_rebase_v6.6_LTS
        git checkout 116fbf86655bcc669b416defceabf085291f4500
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        make W=1 O=build_dir ARCH=i386 olddefconfig
        make W=1 O=build_dir ARCH=i386 SHELL=/bin/bash