Add factory to ConfigToolDependency
Add factory to ConfigToolDependency

Some dependencies can be detected multiple ways, such as a config tool
and pkg-config. For pkg-config a new PkgConfigDependency is created and
used to check for the dependency, config tool dependencies are handled
ad-hoc. This allows the ConfigToolDependency to be used in the same way
that PkgConfigDependency is.

jeandet/meson,jeandet/meson,QuLogic/meson,pexip/meson,trhd/meson,ernestask/meson,mesonbuild/meson,ernestask/meson,ernestask/meson,becm/meson,becm/meson,MathieuDuponchelle/meson,becm/meson,MathieuDuponchelle/meson,jeandet/meson,pexip/meson,QuLogic/meson,mesonbuild/meson,pexip/meson,ernestask/meson,QuLogic/meson,trhd/meson,jeandet/meson,jpakkane/meson,becm/meson,jpakkane/meson,MathieuDuponchelle/meson,mesonbuild/meson,jeandet/meson,trhd/meson,thiblahute/meson,jeandet/meson,thiblahute/meson,MathieuDuponchelle/meson,ernestask/meson,MathieuDuponchelle/meson,trhd/meson,thiblahute/meson,jpakkane/meson,mesonbuild/meson,becm/meson,pexip/meson,becm/meson,jpakkane/meson,MathieuDuponchelle/meson,jeandet/meson,thiblahute/meson,MathieuDuponchelle/meson,pexip/meson,pexip/meson,trhd/meson,QuLogic/meson,jpakkane/meson,jpakkane/meson,jpakkane/meson,mesonbuild/meson,ernestask/meson,thiblahute/meson,pexip/meson,trhd/meson,MathieuDuponchelle/meson,becm/meson,mesonbuild/meson,QuLogic/meson,pexip/meson,jpakkane/meson,thiblahute/meson,QuLogic/meson,becm/meson,mesonbuild/meson,QuLogic/meson,jeandet/meson,MathieuDuponchelle/meson,pexip/meson,mesonbuild/meson,mesonbuild/meson,ernestask/meson,jeandet/meson,trhd/meson,ernestask/meson,thiblahute/meson,thiblahute/meson,trhd/meson,trhd/meson,thiblahute/meson,ernestask/meson,becm/meson,pexip/meson,jpakkane/meson,mesonbuild/meson,QuLogic/meson,becm/meson,QuLogic/meson