cmd/go: disable compiler DWARF generation on some platforms

The linker disables DWARF for these platforms.
Given that, we can spare the compiler some work.

Change-Id: Ic5a6b675150aca199bdc1dd2cdf5eeb4e215bdff
Reviewed-on: https://go-review.googlesource.com/40859
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/cmd/go/internal/work/build.go

@@ -2203,7 +2203,8 @@ func (gcToolchain) gc(b *Builder, p *load.Package, archive, obj string, asmhdr b
 	if p.Internal.BuildID != "" {
 		gcargs = append(gcargs, "-buildid", p.Internal.BuildID)
 	}
-	if p.Internal.OmitDebug {
+	platform := cfg.Goos + "/" + cfg.Goarch
+	if p.Internal.OmitDebug || platform == "nacl/amd64p32" || platform == "darwin/arm" || platform == "darwin/arm64" {
 		gcargs = append(gcargs, "-dwarf=false")
 	}