libxml-parser-perl: fix host-intltool breakage when microperl is enabled

Microperl will build host-microperl and install it into HOST_DIR/usr/bin,
where other packages will pick it up as _CONFIGURE_OPTS / _MAKE_ENV
prepends that to the path.

libxml-parser-perl didn't though, so it would still be built against
the system perl, causing host-intltool to fail when it would use
host-microperl together with libxml-parser-perl if the system perl
isn't compatible with host-microperl.

Fix it by using HOST_CONFIGURE_OPTS and ensuring it is built after
(host-)microperl if enabled.

Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>