cmd/go: add error for cross-compiled -race builds

Race builds require C dependencies, but cross-compiled cgo builds are
not always possible, so don't suggest enabling CGO in those cases.

Fixes #37021

Change-Id: I1fd675efc9cef958a926bd63eac8e6858bc59d0a
GitHub-Last-Rev: cbf43c1
GitHub-Pull-Request: #38670
Reviewed-on: https://go-review.googlesource.com/c/go/+/230202
Reviewed-by: Bryan C. Mills <[email protected]>

Author: keyan

src/cmd/go/internal/work/init.go

@@ -16,6 +16,7 @@ import (
 	"fmt"
 	"os"
 	"path/filepath"
+	"runtime"
 	"strings"
 )
 
@@ -84,7 +85,12 @@ func instrumentInit() {
 	modeFlag := "-" + mode
 
 	if !cfg.BuildContext.CgoEnabled {
-		fmt.Fprintf(os.Stderr, "go %s: %s requires cgo; enable cgo by setting CGO_ENABLED=1\n", flag.Args()[0], modeFlag)
+		if runtime.GOOS != cfg.Goos || runtime.GOARCH != cfg.Goarch {
+			fmt.Fprintf(os.Stderr, "go %s: %s requires cgo\n", flag.Args()[0], modeFlag)
+		} else {
+			fmt.Fprintf(os.Stderr, "go %s: %s requires cgo; enable cgo by setting CGO_ENABLED=1\n", flag.Args()[0], modeFlag)
+		}
+
 		base.SetExitStatus(2)
 		base.Exit()
 	}