[driver] fix crash with empty args (fixes
@@ -18,6 +18,7 @@ pub fn parser<'a, 'b>() -> App<'a, 'b> {
.setting(AppSettings::UnifiedHelpMessage)
.setting(AppSettings::GlobalVersion)
.setting(AppSettings::VersionlessSubcommands)
+ .setting(AppSettings::ArgRequiredElseHelp)
.arg(
CodegenOptions::option_group_arg()
.global(true)
