newt: not available for static only builds

newt: not available for static only builds

Fixes:
http://autobuild.buildroot.net/results/a40/a400e1fe7291d3bd3171ad04ce5fd7ba235d39af/
http://autobuild.buildroot.net/results/ec3/ec38d0f1d1faa2a87321bab10f87772eb819adc9/
http://autobuild.buildroot.net/results/7cb/7cbc8cd265d527c7b56d57e511903b23a4a84489/

newt uses autoconf but not automake, and unconditionally tries to build a
.so file - So it doesn't work in static only builds.

The only reverse dependency is network-manager, which already depends on
glibc.

Signed-off-by: Peter Korsgaard <peter@korsgaard.com>