lftp: add missing host-pkgconf dependency

lftp configure.ac uses PKG_CHECK_MODULES, so it must have host-pkgconf
in its dependency, otherwise the autoreconf step fails due to the lack
of pkg.m4.

Fixes:

  http://autobuild.buildroot.org/results/b16/b16d964f275d4d8703665236b969cc19f7ef20be/

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/lftp/lftp.mk

@@ -9,7 +9,7 @@ LFTP_SITE    = http://lftp.yar.ru/ftp
 LFTP_LICENSE = GPLv3+
 LFTP_LICENSE_FILES = COPYING
 LFTP_AUTORECONF = YES
-LFTP_DEPENDENCIES  = readline zlib
+LFTP_DEPENDENCIES = readline zlib host-pkgconf
 
 ifneq ($(BR2_PREFER_STATIC_LIB),y)
 LFTP_CONF_OPT += --with-modules