neardal: properly quote output of pkg-config

Commit 5504039c (neardal: fix readline/libedit detection with static
linking) added the output of pkg-config to the LIBS shell variable without
adding quotes around it, breaking the logic if the output would ever consist
of more than 1 word.

Now, pkg-config --libs ncurses currently only outputs '-lncurses', so
nothing is really broken (for now atleast), but lets add the quotes before
it does or the syntax gets copied somewhere else where it does.

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