Motivation for this change

libircclient does not compile on darwin and caused my unrelated pr check to fail.

Its src/Makefile.in has

libircclient.so: libircclient.o
	$(CC) -shared -s -Wl,-soname,libircclient.so.$(APIVERSION) -o libircclient.so libircclient.o @LDFLAGS@ @LIBS@

which fails with

clang -shared -s -Wl,-soname,libircclient.so.1 -o libircclient.so libircclient.o
ld: warning: option -s is obsolete and being ignored
ld: unknown option: -soname
clang-3.7: error: linker command failed with exit code 1 (use -v to see invocation)

Things done

• Tested using sandboxing
  (nix.useSandbox on NixOS,
  or option build-use-sandbox in nix.conf
  on non-NixOS)
• Built on platform(s)
  • NixOS
  • macOS
  • Linux
• Tested compilation of all pkgs that depend on this change using nix-shell -p nox --run "nox-review wip"
• Tested execution of all binary files (usually in ./result/bin/)
• Fits CONTRIBUTING.md.