enable extra flag

Author: xiazhvera

builder/actions/cmake.py

@@ -143,6 +143,8 @@ def _build_project(env, project, cmake_extra, build_tests=False, args_transforme
                 compiler_flags.append(
                     '-DCMAKE_{}_COMPILER={}'.format(opt.upper(), value))
                 if 'clang-3' in value:
+                    # enable extra compiler flags
+                    compiler_flags.append("-Wextra")
                     compiler_flags.append("-Wno-missing-field-initializers")
     cmake_args = UniqueList([
         "-B{}".format(project_build_dir),