libunistring: host-libunistring is needed by guile

Signed-off-by: Pedro Aguilar <paguilar@paguilar.org>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

package/libunistring/libunistring.mk

@@ -17,3 +17,4 @@ LIBUNISTRING_CONF_OPTS += --disable-threads
 endif
 
 $(eval $(autotools-package))
+$(eval $(host-autotools-package))