go/types/internal/gcimporter: update for 7g and 9g

Change-Id: Ied1582d8aabee2eb346e1c23bfd7781e4a091264
Reviewed-on: https://go-review.googlesource.com/8621Reviewed-by: Robert Griesemer <gri@golang.org>

src/go/types/internal/gcimporter/gcimporter.go

@@ -30,7 +30,7 @@ func init() {
 	types.DefaultImport = Import
 }
 
-var pkgExts = [...]string{".a", ".5", ".6", ".8"}
+var pkgExts = [...]string{".a", ".5", ".6", ".7", ".8", ".9"}
 
 // FindPkg returns the filename and unique package id for an import
 // path based on package information provided by build.Import (using

src/go/types/internal/gcimporter/gcimporter_test.go

@@ -34,20 +34,11 @@ func skipSpecialPlatforms(t *testing.T) {
 var gcPath string // Go compiler path
 
 func init() {
-	// determine compiler
-	var gc string
-	switch runtime.GOARCH {
-	case "386":
-		gc = "8g"
-	case "amd64":
-		gc = "6g"
-	case "arm":
-		gc = "5g"
-	default:
-		gcPath = "unknown-GOARCH-compiler"
+	if char, err := build.ArchChar(runtime.GOARCH); err == nil {
+		gcPath = filepath.Join(build.ToolDir, char+"g")
 		return
 	}
-	gcPath = filepath.Join(build.ToolDir, gc)
+	gcPath = "unknown-GOARCH-compiler"
 }
 
 func compile(t *testing.T, dirname, filename string) string {