Build on OpenBSD 7.0 fails - undefined cxx_throw test_eh_personality

[rmottola]

A fresh build, fresh configured with "ccmake ." yields:

[ 12%] Linking C executable CXXExceptions_legacy_optimised
ld: error: /home/multix/code/gnustep-svc/libobjc2/Build/libobjc.so: undefined reference to cxx_throw() [--no-allow-shlib-undefined]
ld: error: /home/multix/code/gnustep-svc/libobjc2/Build/libobjc.so: undefined reference to test_eh_personality [--no-allow-shlib-undefined]
cc: error: linker command failed with exit code 1 (use -v to see invocation)