zig cc: Add support for -z

This is only the first step; it makes zig cc recognize -z and append it to the linker args, but the linker arg parsing doesn't support -z yet so it will just give the warning 'unsupported linker arg: -z'

src/main.cpp

@@ -737,6 +737,10 @@ static int main0(int argc, char **argv) {
                 case Stage2ClangArgForLinker:
                     linker_args.append(buf_create_from_str(it.only_arg));
                     break;
+                case Stage2ClangArgLinkerInputZ:
+                    linker_args.append(buf_create_from_str("-z"));
+                    linker_args.append(buf_create_from_str(it.only_arg));
+                    break;
             }
         }
         // Parse linker args