qemu: Add packageconfig for libbpf support

qemu: Add packageconfig for libbpf support

its in auto mode, which is troublesome particularly on native recipe
where it pokes at build host to find this library if its not in native
sysroot and when build host has libbpf installed it enables it silently
otherwise disables the support. so lets make it deterministic, and if
one needs to enable this feature then enable the packageconfig
intentionally, It was found when trying to solve this QA warning

Skipping RPATH /usr/lib64 as is a standard search path for /mnt/b/yoe/master/build/tmp/work/x86_64-linux/qemu-system-native/6.2.0-
r0/sysroot-destdir/mnt/b/yoe/master/build/tmp/work/x86_64-linux/qemu-system-native/6.2.0-r0/recipe-sysroot-native/usr/bin/qemu-system-x86_64

This is becasue qemu's build system adds the needed flags to -rpath for
the libraries it needs and in this case it has found libbpf.so in
/usr/lib64 on build host.

Signed-off-by: Khem Raj <raj.khem@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>