package/qemu: disable bzip2 for the host variant

package/qemu: disable bzip2 for the host variant

bzip2 support is needed for reading bzip2-compressed dmg images.

But the host-bzip2 is missing from host qemu package dependency,
so the qemu build system will try to detect automatically the
external libbzip2 libraries installed on the host.

$ ldd output/host/bin/qemu-system-aarch64
	[...]
	libbz2.so.1 => /lib64/libbz2.so.1
or
	libbz2.so.1.0 => output/host/lib/libbz2.so.1.0
if host-bzip2 is built before host-qemu.

Disable explicitely bzip2 options to improve the build
reproducibility.

Signed-off-by: Romain Naour <romain.naour@gmail.com>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>