Meson generates Ninja files. At first, you were supposed to run ninja after Meson yourself but modern Meson support meson compile which calls ninja under the hood
> In contrast to Make, Ninja lacks features such as string manipulation, as Ninja build files are not meant to be written by hand. Instead, a "build generator" should be used to generate Ninja build files. Gyp, CMake, Meson, and gn[9] are popular build management software tools which support creating build files for Ninja.