Something

#create build area in a ramdisk mounted at /usr/src, sync with backed up sources (saving bandwidth, and your time)
function f_begin(){
        if mount | grep "ramfs" | grep -qv "/usr/src"; then
                mount -t ramfs -o size=6gb ramfs /usr/src && echo "ramfs mounted"
                cp -R ${TOOLCHAIN_ARCHIVE}/sources} /usr/src/ && echo "local sources copied to ramfs"
                if [[ `pwd | grep '/usr/src/sources'` = "/usr/src/sources" ]]; then
                        f_begin2
                else
                        echo "run this script at: /usr/src/sources/build-toolchain.sh to continue"
                fi
        fi
}