Added -fno-rtti and -nodefaultlibs for slightly smaller size.
Also added LTO for a close to 25kb size reduction.
Signed-off-by: Rosen Penev <rosenp@gmail.com>
Building unrar together with libunrar creates conflicts that can be fixed by
doing separate builds.
Closes https://github.com/openwrt/packages/pull/2060.
Signed-off-by: Álvaro Fernández Rojas <noltari@gmail.com>