Fix popen PATH for bundle exts depending on brew-installed deps

popen's default PATH evaluated to /opt/homebrew/Library/Homebrew/shims/shared:/usr/bin:/bin:/usr/sbin:/sbin on my system. Note that it does not contain brew's default installation folder. This is a problem when a cmd calls another brew-installed command to do the actual installation, e.g. with the npm bundle extension calling node. Node will not be found in the default PATH, resulting in an error.

This fix makes sure that brew-installed commands can be called from popen-executed commands. The npm bundle extension is broken without this fix.