xinetd: explicitly specify AR in build step

xinetd's configure does not set up an AR variable, and there
are no libtool files to autoreconfigure.  So instead, lets
pass in AR during the build.

Signed-off-by: Danomi Manchego <danomimanchego123@gmail.com>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>