Reading Davids answer, I realize I did not explain well what was the problem. The error occurred during the at the execution of the poudriere testport command, giving a following logfile:
===========================================================================
=>> Recording filesystem state for prebuild... done
=======================<phase: configure >============================
===> renaissanc- depends on executable: gmake - found
===> renaissanc- depends on file: /usr/local/bin/ld.gold - found
===> renaissanc- depends on shared library: libgnustep-base.so - found (/usr/local/GNUstep/System/Library/Libraries/libgnustep-base.so)
===> renaissanc- depends on shared library: libgnustep-gui.so - found (/usr/local/GNUstep/System/Library/Libraries/libgnustep-gui.so)
===> Configuring for renaissanc-
===========================================================================
=======================<phase: build >============================
===> Building for renaissanc-
gmake[1]: Entering directory '/wrkdirs/usr/ports/devel/renaissance/work/libs-renaissance-13bd630'
GNUmakefile:29:
GNUmakefile:30: Unable to obtain GNUSTEP_MAKEFILES setting from gnustep-config!
GNUmakefile:31: Perhaps gnustep-make is not properly installed,
GNUmakefile:32: so gnustep-config is not in your PATH.
GNUmakefile:33:
GNUmakefile:34: Your PATH is currently /wrkdirs/usr/ports/devel/renaissance/work/.bin:/sbin:/bin:/usr/sbin:/usr/bin:/usr/local/sbin:/usr/local/bin:/nonexistent/bin
GNUmakefile:35:
GNUmakefile:40: *** You need to set GNUSTEP_MAKEFILES before compiling!. Stop.
gmake[1]: Leaving directory '/wrkdirs/usr/ports/devel/renaissance/work/libs-renaissance-13bd630'
===> Compilation failed unexpectedly.
Try to set MAKE_JOBS_UNSAFE=yes and rebuild before reporting the failure to
the maintainer.
*** Error code 1
That was solved by adding build to the line: USE_GNUSTEP= base gui build.
Now the next problem has occurred: