| ## Control the number of child processes with an environment variable | |
| Previously, `meson test` checked the `MESON_TESTTHREADS` variable to control | |
| the amount of parallel jobs to run; this was useful when `meson test` is | |
| invoked through `ninja test` for example. With this version, a new variable | |
| `MESON_NUM_PROCESSES` is supported with a broader scope: in addition to | |
| `meson test`, it is also used by the `external_project` module and by | |
| Ninja targets that invoke `clang-tidy`, `clang-format` and `clippy`. |