#### My config ####
meta-neotion$ grep IMAGE_FEATURES conf/distro/neotion.conf recipes-core/images/neotion-ottgw-*
conf/distro/neotion.conf:IMAGE_FEATURES[validitems] += "nfsroot swupdate"
conf/distro/neotion.conf:IMAGE_FEATURES += "nfsroot swupdate"
recipes-core/images/neotion-dev.bb:IMAGE_FEATURES_remove = "swupdate"
recipes-core/images/neotion-prod.bb:IMAGE_FEATURES_remove = "nfsroot"

#### In u-boot-fw-utils .bbappend, i have the following snippet of code ####

do_install_append () {
    install -d ${DEPLOYDIR}
    install -m 755  ${WORKDIR}/boot.ini ${DEPLOYDIR}

    # Debug:
    bbwarn "IMAGE_FEATURES = ${IMAGE_FEATURES}"

    # Prepend nfs=y nfsroot=...
    NFSROOT="${@bb.utils.contains('IMAGE_FEATURES', 'nfsroot', "1", "0", d)}"
    if [ "${NFSROOT}" = 1 ]; then
        bbwarn "nfsroot is set in IMAGE_FEATURES, adapting boot.init..."
        if [ -z "${NFSROOT_PATH}" ]; then
            bberror "NFSROOT_PATH not set in build/conf/local.conf, boot.ini will be bogus !"
        else
            sed -i -e "s#\(ODROIDC2-UBOOT-CONFIG\)#\1\nsetenv nfs \"y\"\nsetenv nfsroot_path \"${NFSROOT_PATH}\"\n#" ${DEPLOYDIR}/boot.ini
        fi
    else
        bbwarn "nfsroot is NOT set in IMAGE_FEATURES, leaving boot.init untouched..."
    fi

}

#### What i run ####
bitbake u-boot-fw-utils:do_cleanall # to make sure bitbake rebuild it
bitbake -DD -v neotion-dev 2>&1 |tee output.log # To save the whole output

#### And it fails ###
~/Work/Fontaine/t55/build-dev$ grep IMAGE_FEA output.log
u-boot-fw-utils-v2015.01+gitAUTOINC+2fcbc68e05-r0 do_install: + bbwarn IMAGE_FEATURES =  nfsroot swupdate debug-tweaks
+ printf %b\0 bbwarn IMAGE_FEATURES =  nfsroot swupdate debug-tweaks
+ bbwarn nfsroot is set in IMAGE_FEATURES, adapting boot.init...
+ printf %b\0 bbwarn nfsroot is set in IMAGE_FEATURES, adapting boot.init...
WARNING: u-boot-fw-utils-v2015.01+gitAUTOINC+2fcbc68e05-r0 do_install: IMAGE_FEATURES =  nfsroot swupdate debug-tweaks
WARNING: u-boot-fw-utils-v2015.01+gitAUTOINC+2fcbc68e05-r0 do_install: nfsroot is set in IMAGE_FEATURES, adapting boot.init...