meson: Fix firewalld check
meson: Fix firewalld check

firewalld is Linux-only, so it should be disabled by default
everywhere else and attempts to explicitly enable firewalld
support on non-Linux targets should result in an error.

Signed-off-by: Andrea Bolognani <3ada0bee826c753786fdbba72243dfba997094cf@redhat.com>
Reviewed-by: Pavel Hrdina <d4772d05997b8abf035041e3b4f4996380ea7e7a@redhat.com>

libvirt/libvirt,zippy2/libvirt,libvirt/libvirt,nertpinx/libvirt,crobinso/libvirt,olafhering/libvirt,olafhering/libvirt,crobinso/libvirt,zippy2/libvirt,nertpinx/libvirt,olafhering/libvirt,nertpinx/libvirt,zippy2/libvirt,crobinso/libvirt,crobinso/libvirt,jfehlig/libvirt,jfehlig/libvirt,zippy2/libvirt,olafhering/libvirt,libvirt/libvirt,jfehlig/libvirt,jfehlig/libvirt,libvirt/libvirt,nertpinx/libvirt,nertpinx/libvirt