build: add GNU install to prerequisites

build: add GNU install to prerequisites

The recent removal of usbutils from core and replacement by hwdata in
packages has exposed hwdata's requirement for certain GNU options on
'install' (-T)  Other packages (sqm-scripts) have openwrt specific
makefile sections to avoid GNU options but I suspect this is going to
get harder in the future.

Add GNU install as a prerequisite and link into
$STAGING_DIR/host/etc/bin as per similar GNU utils

This resolves an issue building under MacOS which would otherwise use a
non-GNU options aware version of 'install'

Signed-off-by: Kevin Darbyshire-Bryant <ldir@darbyshire-bryant.me.uk>