readline: set NCURSES_STATIC for the static build
readline: set NCURSES_STATIC for the static build

ncurses has started to default to dllimport by default, which means
NCURSES_STATIC has to be set by anyone trying to statically build against it
to get the right symbol names.

To keep things simple for use just build twice, once dynamically and
once statically with NCURSES_STATIC set.

Alternative to #2956

Also removes the "RPATH" part, which was copied from Arch, but from what I see
doesn't change anything for us.

waterlan/MSYS2-packages,waterlan/MSYS2-packages,waterlan/MSYS2-packages,JPeterMugaas/MSYS2-packages,waterlan/MSYS2-packages,JPeterMugaas/MSYS2-packages,JPeterMugaas/MSYS2-packages,JPeterMugaas/MSYS2-packages