The MesonProjectManager Plugin should use "meson compile" for builds instead of explicitly invoking ninja

The Meson Plugin explicitly uses ninja for the build step, but the preferred way to do this since meson 0.54 is to use the "meson compile" command - this handles any changes to meson.build, and automatically uses whichever backend has been configured for the project.

This would allow the ninja location configuration to be removed from the meson plugin since that becomes meson's problem.