input_common: ignore some Clang warnings after 5c4774e8

error: unknown warning option '-Werror=unused-but-set-parameter'; did you mean '-Werror=unused-parameter'? [-Werror,-Wunknown-warning-option]
error: unknown warning option '-Werror=unused-but-set-variable'; did you mean '-Werror=unused-const-variable'? [-Werror,-Wunknown-warning-option]