From the meson quickstart:
“The only thing to note is that you need to create a separate build directory. Meson will not allow you to build source code inside your source tree. All build artifacts are stored in the build directory. This allows you to have multiple build trees with different configurations at the same time. This way generated files are not added into revision control by accident.”
autotools lets you build right in the root directory. If you’re using a git clone, or need to build for multiple architectures, this can vex you.
in json-glib, mkdir build, cd build, and try from there…