cmd: Use correct install tool dir with gccgo

When using the go command built from gccgo to build and
    install a go tool, use the value from runtime GCCGOTOOLDIR as
    the install directory.
    
    This also fixes the output from 'go tool' when used with the
    gccgo-built go command, to only include the go tools and not
    other binaries found in the same directory.
    
    Reviewed-on: https://go-review.googlesource.com/16516

From-SVN: r230677

gcc/go/gofrontend/MERGE

@@ -1,4 +1,4 @@
-dfa74d975884f363c74d6a66a37b1703093fdba6
+d52835c9376985f92f35c32af5f1808239981536
 
 The first line of this file holds the git revision number of the last
 merge done from the gofrontend repository.

libgo/go/cmd/go/pkg.go

@@ -785,7 +785,11 @@ func (p *Package) load(stk *importStack, bp *build.Package, err error) *Package
 		if goTools[p.ImportPath] == toTool {
 			// This is for 'go tool'.
 			// Override all the usual logic and force it into the tool directory.
-			p.target = filepath.Join(gorootPkg, "tool", full)
+			if buildContext.Compiler == "gccgo" {
+				p.target = filepath.Join(runtime.GCCGOTOOLDIR, elem)
+			} else {
+				p.target = filepath.Join(gorootPkg, "tool", full)
+			}
 		}
 		if p.target != "" && buildContext.GOOS == "windows" {
 			p.target += ".exe"

libgo/go/cmd/go/tool.go

@@ -39,6 +39,12 @@ var (
 	toolN bool
 )
 
+// List of go tools found in the gccgo tool directory.
+// Other binaries could be in the same directory so don't
+// show those with the 'go tool' command.
+
+var gccgoTools = []string{"cgo", "fix", "cover", "godoc", "vet"}
+
 func init() {
 	cmdTool.Flag.BoolVar(&toolN, "n", false, "")
 }
@@ -146,6 +152,21 @@ func listTools() {
 		if toolIsWindows && strings.HasSuffix(name, toolWindowsExtension) {
 			name = name[:len(name)-len(toolWindowsExtension)]
 		}
-		fmt.Println(name)
+
+		// The tool directory used by gccgo will have other binaries
+		// in additions to go tools.  Only display go tools for this list.
+
+		if buildContext.Compiler == "gccgo" {
+			for _, tool := range gccgoTools {
+				if tool == name {
+					fmt.Println(name)
+				}
+			}
+		} else {
+
+			// Not gccgo, list all the tools found in this dir
+
+			fmt.Println(name)
+		}
 	}
 }