Install Meson and Ninja for building Git

What does this MR do and why?

We have introduced new build infrastructure into Git using the Meson build system. The intent is that Meson will replace autoconf-based and CMake-based builds, and eventually also the Makefile. We want to start dogfooding this build in Gitaly to detect issues and lacking features with the new infrastructure.

Install both Meson and Ninja so that Gitaly can do so.

Fixes #162 (closed).

Checklist

• (If applicable) Add patches if required for upgrading Ruby version in https://gitlab.com/gitlab-org/gitlab-build-images/-/tree/master/patches/ruby.