package/asterisk: fix host build

package/asterisk: fix host build

The host menuselect tool is linked to our host libxml2 library, but it
is missing an RPATH to the host directory.

This is because menuselect does not use automake, so does not inherit
the LDFLAGS from the configure run.

We fix that by simply passing $(HOST_CONFIGURE_OPTS) in the make
environment.

At the same time, we also install the tool in the host directory, even
if not used from there, so that the sanity checks we run are properly
passed.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Cc: Arnout Vandecappelle <arnout@mind.be>
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>