infra: Move --enable/--disable-debug to package/Makefile.in

A lot of packages ignored BR2_ENABLE_DEBUG. This patch simplifies the handling of
this option by adding the corresponding configure option to the global Makefile
for target packages.

For host packages --disable-debug is added to the global Makefile.

Signed-off-by: Bernd Kuhls <bernd.kuhls@t-online.de>
Reviewed-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>