$ cd /usr/pkgsrc/www/firefox
$ make show-options
Any of the following general options may be selected:
        debug    Enable debugging facilities in the package.
        mozilla-single-profile  Enable single profiles on mozilla browsers
        official-mozilla-branding

These options are enabled by default:

These options are currently enabled:
        official-mozilla-branding

You can select which build options to use by setting PKG_DEFAULT_OPTIONS
or PKG_OPTIONS.gecko.