For some reason, you're missing all your executables (not just weewxd).
I am not familiar with pipenv (I use pyenv). I find it curious that the pipenv version of Python went looking for weewxd in '/Users/mbp/gitRepo/weewx/./bin/weewxd', which, presumably, is in a git repository. Where did it get that idea?
I'm just fishing here, but perhaps the executables got installed in the virtual environment? Perhaps in /Users/mbp/.local/share/virtualenvs/weewx-qjcRhtQ2/bin?
Maybe this is standard behavior for pipenv, maybe it's not. If it is, I wouldn't bother running setup.py: just run everything from whatever directory you unpacked the tar file. Setup.py isn't really necessary. For example, if you're familiar with git, and if you keep repos in ~/gitRepo, you could clone weewx into ~/gitRepo (if you haven't done that already), and run weewx from there. Here's an example:
cd ~/gitRepo
# If you don't already have weewx, clone it:
cd weewx
# Check out the current release:
git checkout v4.8.0
pipenv run python ./bin/wee_config --reconfigure
pipenv run python ./bin/weewxd
There are many other alternatives. The point being that because WeeWX is pure python, nothing needs to be compiled. You can run it from anywhere.
Or, maybe I don't understand pipenv and none of this is necessary.
-tk