Install script fails on default macOS due to lack of /usr/local/bin directory
Linuxes usually have a /usr/local/bin directory by default whereas macOS does not. The install script should ensure that his directory exist before trying to install Site.js into it. Otherwise, it will fail on a default macOS install.
(Since many developer tools create this directory, it got past our testing so far.)
Reported by: Carmen Minikus.