Completion files are not installed to Homebrew Cellar

[Myridium]

$ make install PREFIX="$(brew --cellar)/passage/dev"
install: mkdir /opt/homebrew/Cellar/passage
install: mkdir /opt/homebrew/Cellar/passage/dev
install: mkdir /opt/homebrew/Cellar/passage/dev/lib
install: mkdir /opt/homebrew/Cellar/passage/dev/lib/passage
install: src/platform/darwin.sh -> /opt/homebrew/Cellar/passage/dev/lib/passage/platform.sh
install: mkdir /opt/homebrew/Cellar/passage/dev/lib/passage/extensions
install: mkdir /opt/homebrew/Cellar/passage/dev/bin
install: src/.passage -> /opt/homebrew/Cellar/passage/dev/bin/passage

[FiloSottile]

Hmm, that's because autodetection is looking inside the prefix, which doesn't work with Homebrew's symlinking approach.

https://github.com/FiloSottile/passage/blob/a42b9c117ac823554ba127a814c297d0aeaaef45/Makefile#L8-L10

The best solution might be to just autodetect installation to the Homebrew Cellar.