package/libldns: Fix static build

package/libldns: Fix static build

http://autobuild.buildroot.net/results/a0e/a0e686cbe5104f48c9ab05aef7b2989abdb23821/
http://autobuild.buildroot.net/results/527/527b6167fcade1333d8bedffca21e32e410ed8c9/
http://autobuild.buildroot.net/results/0f2/0f229b6806b5cf18d5b56f80088bba7dc3c6eb28/
http://autobuild.buildroot.net/results/bad/bad1c0590868c1e97f647172f85b112ff2604994/
http://autobuild.buildroot.net/results/7db/7dba36ae44560e65a00daf912abe8b43fa8a060d/
http://autobuild.buildroot.net/results/3bf/3bf24e3e845ad8ebcfd0469787e7b7342ecfe3c5/
http://autobuild.buildroot.net/results/7c6/7c6985518bb068ef1764dfb44c59c9f583f07c71/
http://autobuild.buildroot.net/results/211/2117de3dc3d1168bdba0c771b54b3d998e3d62ce/
http://autobuild.buildroot.net/results/908/90893b2cdbbc02d75be5cbc09b8a244d5b05d386/

[Peter:
 - Move workaround under openssl conditional
 - Only add host-pkgconf for static builds
 - Always use lib target]
Signed-off-by: Bernd Kuhls <bernd.kuhls@t-online.de>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>