DragonFly builds two compilers by default. If you weren’t interesting in building both, there were switches to build only the default, like NO_GCC47. This changed with every compiler update.
With the switch to GCC 5, the new switch is “NO_ALTCOMPILER”. That will last through compiler changes. I’m mentioning this now because sooner or later, you’ll want to gain back some time on a buildworld.
Since there is no GCC 5.0 but GCC 5.1 all related constants should be called gcc51, cc51, etc. instead of gcc50, cc50 isn’t it?