message: Do not shallow-clone and use a specific commit
diff: @@ -19,7 +19,6 @@ ExternalProject_add(
  mavlink
  GIT_REPOSITORY https://github.com/mavlink/mavlink
  GIT_TAG 3b52eac09c2e37325e4bc49cd2667ea37bf1d7d2
  - GIT_SHALLOW TRUE
  PREFIX mavlink
  CONFIGURE_COMMAND Python3::Interpreter
  -m pymavlink.tools.mavgen
  