ports/144139: failure in building x11/xscreensaver-gnome

[Tsurutani Naoki]

mezz at FreeBSD.org wrote:

> We don't support custom CFLAGS. The default is: -O2 -fno-strict-aliasing -pipe
> 
> The '-fno-strict-aliasing' is a must. If you want to do the custom CFLAGS,
> you have to fix the bug by yourself.

make.conf(5) says "Optimization levels other than -O and -O2 are not supported".
If any CFLAGS are not supported, you should not allow setting them in make.conf,
or at least refer to that fact.
If this is the problem specific to this port, port should check CFLAGS in Makefile, 
or add any messages to users to change CFLAGS only while building this port.