OpenBSD includes gcc4 in the base install, which is gcc-4.2.1. If you prefer to use gcc-11.2.0, the names of the binaries differ.

The following are part of gcc-11.2.0:

The following are part of gcc-4.2.1

GNUstep is available if you would like to develop using Objective-C. The following should be added to ~/.kshrc:

export GNUSTEP_MAKEFILES=/usr/local/share/GNUstep/Makefiles
. /usr/local/share/GNUstep/Makefiles/GNUstep.sh

You will also need to call gmake rather than make when building Objective-C code. See this StackOverflow post for more information.