cmd/go, go/build: add support for gccgo tooldir

The gccgo toolchain does not put tools (cgo, vet, etc.) in
$GOROOT/pkg/tool, but instead in a directory available at
runtime.GCCGOTOOLDIR.

Update the go/build package and the cmd/go tool to use this tool
directory when using gccgo.

Change-Id: Ib827336ff53601208300aceb77f76c2e1b069859
Reviewed-on: https://go-review.googlesource.com/111097
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

1 files changed, 13 insertions, 5 deletions

diff --git a/src/cmd/go/internal/cfg/cfg.go b/src/cmd/go/internal/cfg/cfg.go
index 85494e34f0..3df5905d02 100644
--- a/src/cmd/go/internal/cfg/cfg.go
+++ b/src/cmd/go/internal/cfg/cfg.go
@@ -93,11 +93,14 @@ 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().
-	build.ToolDir = filepath.Join(GOROOT, "pkg/tool/"+runtime.GOOS+"_"+runtime.GOARCH)
+	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)
+	}
 }
 
 func findGOROOT() string {
@@ -105,6 +108,11 @@ func findGOROOT() string {
 		return filepath.Clean(env)
 	}
 	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()
 	if err == nil {
 		exe, err = filepath.Abs(exe)