When behind a corporate proxy, one often needs to specify `HTTP_PROXY` and `HTTPS_PROXY` for some command line tools to work properly. However, `pacman` seems to rely on the lowercase equivalent environment variables. In a Windows command prompt environment, it is not possible to set both since Windows environment variables are not case-sensitive. As a workaround, this build script checks for the existence of HTTP_PROXY and HTTPS_PROXY. If they exist, they are exported as lowercase variables.
