cmd: enable android/386 build (buildmode=pie by default)

no buildmode=c-shared yet.

Update golang/go#9327.

Change-Id: I9989d954d574807bac105da401c3463607fe8a99
Reviewed-on: https://go-review.googlesource.com/16700Reviewed-by: David Crawshaw <crawshaw@golang.org>

src/cmd/compile/internal/gc/lex.go

@@ -222,7 +222,7 @@ func Main() {
 	var flag_shared int
 	var flag_dynlink bool
 	switch Thearch.Thechar {
-	case '5', '6', '7', '9':
+	case '5', '6', '7', '8', '9':
 		obj.Flagcount("shared", "generate code that can be linked into a shared library", &flag_shared)
 	}
 	if Thearch.Thechar == '6' {

src/cmd/go/build.go

@@ -361,7 +361,7 @@ func buildModeInit() {
 		ldBuildmode = "c-shared"
 	case "default":
 		switch platform {
-		case "android/arm", "android/arm64", "android/amd64":
+		case "android/arm", "android/arm64", "android/amd64", "android/386":
 			codegenArg = "-shared"
 			ldBuildmode = "pie"
 		default:
@@ -375,7 +375,8 @@ func buildModeInit() {
 			fatalf("-buildmode=pie not supported by gccgo")
 		} else {
 			switch platform {
-			case "linux/arm", "android/arm", "linux/amd64", "android/amd64", "linux/arm64", "android/arm64", "linux/ppc64le":
+			case "linux/amd64", "linux/arm", "linux/arm64", "linux/ppc64le",
+				"android/amd64", "android/arm", "android/arm64", "android/386":
 				codegenArg = "-shared"
 			default:
 				fatalf("-buildmode=pie not supported on %s\n", platform)