sys-apps/file-4.23; libtool: link: cannot determine absolute directory name of `usr/lib'

[Viridior]

[environment]
$ROOT: /usr/armv7a-softfloat-linux-gnueabi/
$SYSROOT: /usr/armv7a-softfloat-linux-gnueabi/
$PORTAGE_CONFIGROOT: /usr/armv7a-softfloat-linux-gnueabi/
$CBUILD: i686-pc-linux-gnu

[software]
sys-apps/file-4.26

[command]
$ACCEPT_KEYWORDS="x86 ~x86 arm ~arm" cross-emerge sys-apps/file

[error]
../libtool: line 1887: cd: usr/lib: No such file or directory
libtool: link: cannot determine absolute directory name of `usr/lib'
make[2]: *** [libmagic.la] Error 1
make[2]: Leaving directory `/var/tmp/portage/sys-apps/file-4.26/work/file-4.26/src'
make[1]: *** [all-recursive] Error 1
make[1]: Leaving directory `/var/tmp/portage/sys-apps/file-4.26/work/file-4.26'
make: *** [all] Error 2

[discussion]
Common error found while cross-compiling.

[Viridior (jacobgalbreath)]

must add ROOT="/usr/${CHOST}" variable to make.conf, portage does not necessarily use global env variable