Add note about using Ninja on old Meson versions. [skip ci]
Add note about using Ninja on old Meson versions. [skip ci]

pexip/meson,QuLogic/meson,QuLogic/meson,mesonbuild/meson,jpakkane/meson,pexip/meson,QuLogic/meson,pexip/meson,jpakkane/meson,jpakkane/meson,mesonbuild/meson,jpakkane/meson,mesonbuild/meson,jpakkane/meson,jpakkane/meson,jpakkane/meson,pexip/meson,pexip/meson,pexip/meson,jpakkane/meson,mesonbuild/meson,QuLogic/meson,QuLogic/meson,mesonbuild/meson,pexip/meson,pexip/meson,mesonbuild/meson,mesonbuild/meson,QuLogic/meson,mesonbuild/meson,jpakkane/meson,QuLogic/meson,pexip/meson,QuLogic/meson,QuLogic/meson,mesonbuild/meson,pexip/meson,mesonbuild/meson