cmd/go: fix incorrect determining default value of CGO_ENABLED

The default value is the value obtained when
no environment variables are set and go env  -w is not used.

In the past,
we used the current value
(may be modified by an environment variable to a non-default value),
error was used as the default value.

For #69994

Change-Id: Iead3a6cacd04dc51a094ffb9f7bb7553320fcd78
Reviewed-on: https://go-review.googlesource.com/c/go/+/621995
Reviewed-by: Michael Matloob <matloob@golang.org>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Michael Matloob <matloob@google.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>

3 files changed, 2 insertions, 18 deletions

diff --git a/src/cmd/dist/build.go b/src/cmd/dist/build.go
index aa106e45c5..b50f3342fe 100644
--- a/src/cmd/dist/build.go
+++ b/src/cmd/dist/build.go
@@ -673,7 +673,6 @@ var gentab = []struct {
 	file string
 	gen  func(dir, file string)
 }{
-	{"go/build", "zcgo.go", mkzcgo},
 	{"cmd/go/internal/cfg", "zdefaultcc.go", mkzdefaultcc},
 	{"internal/runtime/sys", "zversion.go", mkzversion},
 	{"time/tzdata", "zzipdata.go", mktzdata},
diff --git a/src/cmd/dist/buildgo.go b/src/cmd/dist/buildgo.go
index 884e9d729a..6bd8a9ce8d 100644
--- a/src/cmd/dist/buildgo.go
+++ b/src/cmd/dist/buildgo.go
@@ -7,7 +7,6 @@ package main
 import (
 	"fmt"
 	"io"
-	"os"
 	"path/filepath"
 	"sort"
 	"strings"
@@ -108,22 +107,6 @@ func defaultCCFunc(name string, defaultcc map[string]string) string {
 	return buf.String()
 }
 
-// mkzcgo writes zcgo.go for the go/build package:
-//
-//	package build
-//	const defaultCGO_ENABLED = <CGO_ENABLED>
-//
-// It is invoked to write go/build/zcgo.go.
-func mkzcgo(dir, file string) {
-	var buf strings.Builder
-	writeHeader(&buf)
-	fmt.Fprintf(&buf, "package build\n")
-	fmt.Fprintln(&buf)
-	fmt.Fprintf(&buf, "const defaultCGO_ENABLED = %s\n", quote(os.Getenv("CGO_ENABLED")))
-
-	writefile(buf.String(), file, writeSkipSame)
-}
-
 // mktzdata src/time/tzdata/zzipdata.go:
 //
 //	package tzdata
diff --git a/src/cmd/dist/buildruntime.go b/src/cmd/dist/buildruntime.go
index 04b5b45410..87e8867176 100644
--- a/src/cmd/dist/buildruntime.go
+++ b/src/cmd/dist/buildruntime.go
@@ -6,6 +6,7 @@ package main
 
 import (
 	"fmt"
+	"os"
 	"strings"
 )
 
@@ -66,6 +67,7 @@ func mkbuildcfg(file string) {
 	fmt.Fprintf(&buf, "const defaultGOOS = runtime.GOOS\n")
 	fmt.Fprintf(&buf, "const defaultGOARCH = runtime.GOARCH\n")
 	fmt.Fprintf(&buf, "const DefaultGOFIPS140 = `%s`\n", gofips140)
+	fmt.Fprintf(&buf, "const DefaultCGO_ENABLED = %s\n", quote(os.Getenv("CGO_ENABLED")))
 
 	writefile(buf.String(), file, writeSkipSame)
 }