Using
portmaster -aD over the past few days, I started getting error messages from some port builds such as x11-toolkits/gtksourceview2 saying they needed to be recompiled with the -fPIC flag. Instead, it turns out that I needed to comment out the ccache related items in /etc/make.conf, then install textproc/xmlto. After that I uncommented the ccache items and portmaster -aD ran smoothly. It wasn't necessary to add the -fPIC flag to make.conf.