build: support explicitly disabling netcf
build: support explicitly disabling netcf

placing "-Dnetcf=disabled" on the meson commandline was ignored,
meaning that even with that option the build would get WITH_NETCF if
the netcf-devel package was found - the only way to disable it was to
uninstall netcf-devel.

This patch adds the small bit of logic to check the netcf meson
commandline option (in addition to whether netcf-devel is installed)
before defining WITH_NETCF.

Signed-off-by: Laine Stump <c23361c43fbf79fed83e8b76173707b083d6caf5@redhat.com>
Reviewed-by: Neal Gompa <8135daa3762340227c0c67f1c47ad07a127bd3a3@gmail.com>
Reviewed-by: Michal Privoznik <83d82aaba2eed257f4814b0c239c260c4caaadf0@redhat.com>

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