icu: speed up host build

The host build of icu doesn't need to build everything, so we can add
a few more --disable-<foo> options to save a little bit of build time.

On a fast build server, this bring the host icu build from 2m28.517s
to 2m5.192s.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>