Update meson.build and add wrapfiles so that all dependencies are
handled as subprojects.

This allows builds completely outside of bitbake or an SDK.

Tested: built phosphor-debug-collector repo successfully using
        `meson -Dtests build`.

Signed-off-by: George Liu <liuxiwei@inspur.com>
Change-Id: I51bae90f4fac113270e259b7acac3630b5ec6778