cmd/distpack: don't keep the pack tool

This was an oversight: the pack tool isn't actually used in builds.

For #71867

Change-Id: Ib1f1cce0b574cf1d2c1002b2f2ab9ef9d750d0fb
Reviewed-on: https://go-review.googlesource.com/c/go/+/677557
Reviewed-by: Michael Matloob <[email protected]>
LUCI-TryBot-Result: Go LUCI <[email protected]>
Reviewed-by: Michael Pratt <[email protected]>
Reviewed-by: Dmitri Shuralyov <[email protected]>

Author: matloob

src/cmd/distpack/pack.go

@@ -171,7 +171,7 @@ func main() {
 			switch strings.TrimSuffix(path.Base(name), ".exe") {
 			default:
 				return false
-			case "asm", "cgo", "compile", "cover", "link", "pack", "preprofile", "vet":
+			case "asm", "cgo", "compile", "cover", "link", "preprofile", "vet":
 			}
 		}
 		return true

src/cmd/go/internal/work/gc.go

@@ -482,7 +482,7 @@ func (gcToolchain) pack(b *Builder, a *Action, afile string, ofiles []string) er
 	p := a.Package
 	sh := b.Shell(a)
 	if cfg.BuildN || cfg.BuildX {
-		cmdline := str.StringList(base.Tool("pack"), "r", absAfile, absOfiles)
+		cmdline := str.StringList("go", "tool", "pack", "r", absAfile, absOfiles)
 		sh.ShowCmd(p.Dir, "%s # internal", joinUnambiguously(cmdline))
 	}
 	if cfg.BuildN {