refactor: use go:linkname to link internal/platform.CgoSupported

Instead of creating a custom platform package, use the go:linkname
directive to directly link to Go's standard library internal/platform.CgoSupported
function. This approach:

- Eliminates the need to maintain a copy of platform support data
- Uses Go's canonical platform information directly
- Reduces code duplication and maintenance burden
- Follows Go's linkname pattern for accessing internal packages

Changes:
- Added import _ "unsafe" to enable linkname
- Added //go:linkname directive for cgoSupported function
- Removed custom runtime/internal/lib/internal/platform package
- Updated function call from platform.CgoSupported to cgoSupported

🤖 Generated with [codeagent](https://github.com/qbox/codeagent)
Co-authored-by: luoliwoshang <luoliwoshang@users.noreply.github.com>

runtime/internal/lib/go/build/build.go

@@ -14,8 +14,7 @@ import (
 	"runtime"
 	"strconv"
 	"strings"
-
-	"github.com/goplus/llgo/runtime/internal/lib/internal/platform"
+	_ "unsafe"
 )
 
 // Type aliases to reference standard library types
@@ -79,7 +78,7 @@ func defaultContext() Context {
 		c.CgoEnabled = false
 	default:
 		if runtime.GOARCH == c.GOARCH && runtime.GOOS == c.GOOS {
-			c.CgoEnabled = platform.CgoSupported(c.GOOS, c.GOARCH)
+			c.CgoEnabled = cgoSupported(c.GOOS, c.GOARCH)
 			break
 		}
 		c.CgoEnabled = false
@@ -122,3 +121,6 @@ func buildToolTags() []string {
 		"goexperiment.boringcrypto", // Default boring crypto experiment
 	}
 }
+
+//go:linkname cgoSupported internal/platform.CgoSupported
+func cgoSupported(goos, goarch string) bool

runtime/internal/lib/internal/platform/platform.go

@@ -1,65 +0,0 @@
-// Copyright 2024 The GoPlus Authors (goplus.org). All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-// Package platform provides platform-specific utilities.
-package platform
-
-// llgo:skipall
-type _platform struct{}
-
-// An OSArch is a pair of GOOS and GOARCH values indicating a platform.
-type OSArch struct {
-	GOOS, GOARCH string
-}
-
-func (p OSArch) String() string {
-	return p.GOOS + "/" + p.GOARCH
-}
-
-// osArchInfo describes information about an OSArch.
-type osArchInfo struct {
-	CgoSupported bool
-	FirstClass   bool
-	Broken       bool
-}
-
-// distInfo maps OSArch to information about cgo support.
-// This is a simplified version covering the most common platforms.
-var distInfo = map[OSArch]osArchInfo{
-	{"darwin", "amd64"}:   {CgoSupported: true, FirstClass: true},
-	{"darwin", "arm64"}:   {CgoSupported: true, FirstClass: true},
-	{"linux", "386"}:      {CgoSupported: true, FirstClass: true},
-	{"linux", "amd64"}:    {CgoSupported: true, FirstClass: true},
-	{"linux", "arm"}:      {CgoSupported: true, FirstClass: true},
-	{"linux", "arm64"}:    {CgoSupported: true, FirstClass: true},
-	{"linux", "ppc64le"}:  {CgoSupported: true},
-	{"linux", "riscv64"}:  {CgoSupported: true},
-	{"linux", "s390x"}:    {CgoSupported: true},
-	{"windows", "386"}:    {CgoSupported: true, FirstClass: true},
-	{"windows", "amd64"}:  {CgoSupported: true, FirstClass: true},
-	{"windows", "arm64"}:  {CgoSupported: true},
-	{"freebsd", "386"}:    {CgoSupported: true},
-	{"freebsd", "amd64"}:  {CgoSupported: true},
-	{"freebsd", "arm"}:    {CgoSupported: true},
-	{"freebsd", "arm64"}:  {CgoSupported: true},
-	{"openbsd", "386"}:    {CgoSupported: true},
-	{"openbsd", "amd64"}:  {CgoSupported: true},
-	{"openbsd", "arm"}:    {CgoSupported: true},
-	{"openbsd", "arm64"}:  {CgoSupported: true},
-	{"netbsd", "386"}:     {CgoSupported: true},
-	{"netbsd", "amd64"}:   {CgoSupported: true},
-	{"netbsd", "arm"}:     {CgoSupported: true},
-	{"netbsd", "arm64"}:   {CgoSupported: true},
-	{"android", "386"}:    {CgoSupported: true},
-	{"android", "amd64"}:  {CgoSupported: true},
-	{"android", "arm"}:    {CgoSupported: true},
-	{"android", "arm64"}:  {CgoSupported: true},
-	{"illumos", "amd64"}:  {CgoSupported: true},
-	{"solaris", "amd64"}:  {CgoSupported: true},
-}
-
-// CgoSupported reports whether goos/goarch supports cgo.
-func CgoSupported(goos, goarch string) bool {
-	return distInfo[OSArch{goos, goarch}].CgoSupported
-}