What do you mean by winning? I haven't heard of Meson until the last few weeks, and I haven't seen it consumed by any open source projects on GitHub, although my search biases more towards JVM things anyways.
> it only depends on python3 & ninja
I don't see how depending on both Python3 and Ninja is any less dependencies than the JVM. Python3 isn't really available by default on most distributions (maybe that is changing soon), so there is still the overhead of installing it, right? Public CI systems like Travis CI and Circle CI have images that make having a JDK easy.