meson: add dependency for nlohmann-json

nlohmann-json is not always installed, especially when developers are
attempting to do out-of-Docker builds.  Meson subprojects are the
method we use to handle this case.  Add the meson subproject wrap and
appropriate dependency values in the meson.build files.

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: Id855f8e320d9ab9332a3803f6ab0dff3aebfd39b
2 files changed