debug/gdb: install dependable libs in a generic target static libs dir

For now, ncurses is the only dependable target library built for gdb.
But expat is coming, and there's no reason to install each library in
its own place.

So, install ncurses in a generic directory, where other dependable
libraries can be installed as well.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@anciens.enib.fr>

This is NOT the official version of dialog.  This version has been

significantly modified from the original.  It is for use by the Linux

kernel configuration script.  Please do not bother Savio Lam with 

questions about this program.