debug/gdb: Fix compilation for Mingw hosts

GDB requires PDcurses instead of ncurses while running on Windows.
So, do not always compile ncurses in case GDB needs to build.

PDcurses is provided by an earlier build step and is not described in
this file.

Signed-off-by: Remy Bohmer <linux@bohmer.net>
[yann.morin.1998@anciense.nib.fr: we already have a way to detect ncurses usage]
Signed-off-by: "Yann E. MORIN" <yann.morin.1998@anciens.enib.fr>

# Dummy config file to not use a C library *at all*

# depends on BARE_METAL

config LIBC_none

    help

      Do not use a C library.

      This is usefull if your project is self-contained, does not rely on

      an external C library, and provides all the necessary bits.

      Most probably usefull to bootloaders, as they generally don't depend

      on the C library.

      If unsure: do *not* choose that, and use another option in the choice.