if !strings.HasPrefix(arg, "-O") {
			nargs = append(nargs, arg)
		}
	}

	// Force -O0 optimization and append extra arguments, but keep the
	// trailing "-" at the end.
	li := len(nargs) - 1
	last := nargs[li]
	nargs[li] = "-O0"
	nargs = append(nargs, extraArgs...)
	nargs = append(nargs, last)

	if *debugGcc {
		fmt.Fprintf(os.Stderr, "$ %s <<EOF\n", strings.Join(nargs, " "))

			stdPackages: stdPackages,
			importMap:   importMap,
			importDir:   importDir,
		}
		imports, _ = listCache.LoadOrStore(name, imports)
	}

	li := imports.(listImports)
	w.stdPackages = li.stdPackages
	w.importDir = li.importDir
	w.importMap = li.importMap
}

// listEnv returns the process environment to use when invoking 'go list' for
// the given context.
func listEnv(c *build.Context) []string {