neardal: fix readline/libedit detection with static linking

Fixes:
http://autobuild.buildroot.net/results/c3e/c3ea67d9b341749b9591451da3f3b0cb4a9fbb74/
http://autobuild.buildroot.net/results/586/586fa95149aa37df7ef430e3a47a3418e6f7ed97/
http://autobuild.buildroot.net/results/3ea/3eabd3a2cea0d5863b1c0dd8f55c73f34a684f79/



Both readline and libedit link with ncurses but the configure script forgets
to take that into account, causing the detection to fail when linking
statically.

Fix it by using pkg-config to add the needed linker options for ncurses.

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