cmd/go: update to match recent changes to gc

In https://golang.org/cl/111097 the gc version of cmd/go was updated
    to include some gofrontend-specific changes. The gofrontend code
    already has different versions of those changes; this CL makes the
    gofrontend match the upstream code.
    
    Reviewed-on: https://go-review.googlesource.com/111099

From-SVN: r259918

gcc/go/gofrontend/MERGE

@@ -1,4 +1,4 @@
-85ca682349af2cb1aa6b1eecac794aeb73d24f15
+bf6f714559bd7b27b7686811aaf0f6e8e7f1c0d5
 
 The first line of this file holds the git revision number of the last
 merge done from the gofrontend repository.

libgo/go/cmd/go/alldocs.go

@@ -1266,6 +1266,9 @@
 //
 // Special-purpose environment variables:
 //
+// 	GCCGOTOOLDIR
+// 		If set, where to find gccgo tools, such as cgo.
+// 		The default is based on how gccgo was configured.
 // 	GOROOT_FINAL
 // 		The root of the installed Go tree, when it is
 // 		installed in a location other than where it is built.
@@ -1279,9 +1282,6 @@
 // 		Defined by Git. A colon-separated list of schemes that are allowed to be used
 // 		with git fetch/clone. If set, any scheme not explicitly mentioned will be
 // 		considered insecure by 'go get'.
-//	GCCGOTOOLDIR
-//		If set, where to find gccgo tools, such as cgo.
-//		The default is based on how gccgo was configured.
 //
 //
 // Import path syntax

libgo/go/cmd/go/internal/cfg/cfg.go

@@ -92,11 +92,12 @@ var (
 // Update build context to use our computed GOROOT.
 func init() {
 	BuildContext.GOROOT = GOROOT
-	// Note that we must use runtime.GOOS and runtime.GOARCH here,
-	// as the tool directory does not move based on environment variables.
-	// This matches the initialization of ToolDir in go/build,
-	// except for using GOROOT rather than runtime.GOROOT().
 	if runtime.Compiler != "gccgo" {
+		// Note that we must use runtime.GOOS and runtime.GOARCH here,
+		// as the tool directory does not move based on environment
+		// variables. This matches the initialization of ToolDir in
+		// go/build, except for using GOROOT rather than
+		// runtime.GOROOT.
 		build.ToolDir = filepath.Join(GOROOT, "pkg/tool/"+runtime.GOOS+"_"+runtime.GOARCH)
 	}
 }
@@ -107,6 +108,8 @@ func findGOROOT() string {
 	}
 	def := filepath.Clean(runtime.GOROOT())
 	if runtime.Compiler == "gccgo" {
+		// gccgo has no real GOROOT, and it certainly doesn't
+		// depend on the executable's location.
 		return def
 	}
 	exe, err := os.Executable()

libgo/go/cmd/go/internal/help/helpdoc.go

@@ -526,6 +526,9 @@ Architecture-specific environment variables:
 
 Special-purpose environment variables:
 
+	GCCGOTOOLDIR
+		If set, where to find gccgo tools, such as cgo.
+		The default is based on how gccgo was configured.
 	GOROOT_FINAL
 		The root of the installed Go tree, when it is
 		installed in a location other than where it is built.
@@ -539,9 +542,6 @@ Special-purpose environment variables:
 		Defined by Git. A colon-separated list of schemes that are allowed to be used
 		with git fetch/clone. If set, any scheme not explicitly mentioned will be
 		considered insecure by 'go get'.
-	GCCGOTOOLDIR
-		If set, where to find gccgo tools, such as cgo.
-		The default is based on how gccgo was configured.
 	`,
 }
 

libgo/go/cmd/go/internal/load/pkg.go

@@ -13,7 +13,6 @@ import (
 	"os"
 	pathpkg "path"
 	"path/filepath"
-	"runtime"
 	"sort"
 	"strings"
 	"unicode"
@@ -976,7 +975,7 @@ func (p *Package) load(stk *ImportStack, bp *build.Package, err error) {
 			// This is for 'go tool'.
 			// Override all the usual logic and force it into the tool directory.
 			if cfg.BuildToolchainName == "gccgo" {
-				p.Target = filepath.Join(runtime.GCCGOTOOLDIR, elem)
+				p.Target = filepath.Join(base.ToolDir, elem)
 			} else {
 				p.Target = filepath.Join(cfg.GOROOTpkg, "tool", full)
 			}

libgo/go/go/build/build.go

@@ -1595,14 +1595,7 @@ func init() {
 	}
 }
 
-func getToolDir() string {
-	if runtime.Compiler == "gccgo" {
-		return envOr("GCCGOTOOLDIR", runtime.GCCGOTOOLDIR)
-	} else {
-		return filepath.Join(runtime.GOROOT(), "pkg/tool/"+runtime.GOOS+"_"+runtime.GOARCH)
-	}
-}
-
+// ToolDir is the directory containing build tools.
 var ToolDir = getToolDir()
 
 // IsLocalImport reports whether the import path is

libgo/go/go/build/gc.go

@@ -0,0 +1,17 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build gc
+
+package build
+
+import (
+	"path/filepath"
+	"runtime"
+)
+
+// getToolDir returns the default value of ToolDir.
+func getToolDir() string {
+	return filepath.Join(runtime.GOROOT(), "pkg/tool/"+runtime.GOOS+"_"+runtime.GOARCH)
+}

libgo/go/go/build/gccgo.go

@@ -0,0 +1,14 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build gccgo
+
+package build
+
+import "runtime"
+
+// getToolDir returns the default value of ToolDir.
+func getToolDir() string {
+	return envOr("GCCGOTOOLDIR", runtime.GCCGOTOOLDIR)
+}