CURRENT_UID is set in the docker container launch script, this should be unnecessary and is potentially harmful

The lines:

CXX_DEVELOPER_UID=$(stat --printf="%u" /eiron)
CXX_DEVELOPER_GID=$(stat --printf="%g" /eiron)

Should ALWAYS pick out the uid and gid of the project root dir and set the developers uid and gid to be the same. The EXTERNAL_UID trick should never be necessary, and setting the directory's permissions from inside the container is problematic, since now we're affecting the file system permissions on the host system, which breaks the rule of least surprise and can lead to frustration if broken.

If the UID and GID setting does not work on Mac, the calls to stat should be debugged and we need to figure out why the file system does not behave as expected. The bug in the uid query should be fixed, rather than bypassing the query.