cmd/compile, cmd/go: enable -buildmode=shared and related flags on linux/arm

Change-Id: I20840632771a250fb279df64d394135994482af8
Reviewed-on: https://go-review.googlesource.com/14186Reviewed-by: David Crawshaw <crawshaw@golang.org>

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

@@ -226,7 +226,7 @@ func Main() {
 	if Thearch.Thechar == '6' {
 		obj.Flagcount("largemodel", "generate code that assumes a large memory model", &flag_largemodel)
 	}
-	if Thearch.Thechar == '6' || Thearch.Thechar == '8' || Thearch.Thechar == '9' {
+	if Thearch.Thechar == '5' || Thearch.Thechar == '6' || Thearch.Thechar == '8' || Thearch.Thechar == '9' {
 		flag.BoolVar(&flag_dynlink, "dynlink", false, "support references to Go symbols defined in other shared libraries")
 	}
 	obj.Flagstr("cpuprofile", "write cpu profile to `file`", &cpuprofile)

src/cmd/go/build.go

@@ -388,7 +388,7 @@ func buildModeInit() {
 			codegenArg = "-fPIC"
 		} else {
 			switch platform {
-			case "linux/386", "linux/amd64":
+			case "linux/386", "linux/amd64", "linux/arm":
 				buildAsmflags = append(buildAsmflags, "-D=shared=1")
 			default:
 				fatalf("-buildmode=shared not supported on %s\n", platform)
@@ -407,7 +407,7 @@ func buildModeInit() {
 			codegenArg = "-fPIC"
 		} else {
 			switch platform {
-			case "linux/386", "linux/amd64":
+			case "linux/386", "linux/amd64", "linux/arm":
 				buildAsmflags = append(buildAsmflags, "-D=shared=1")
 			default:
 				fatalf("-buildmode=shared not supported on %s\n", platform)