cmd/ld: always mark tlsg STLSBSS

Android apps build again.

Defining TLSG in runtime/tls_arm.s gives it the type SNOPTRBSS, so its
type was never being set when GOOS=android. I considered modifying the
if statement, but I no longer understand the intention of the original
change (in d738c6b0). We were always setting it before, what
platform is this not valid for?

Fixes #9829

Change-Id: I3eaa4a9590893eff67695797eb22547a170cdbcd
Reviewed-on: https://go-review.googlesource.com/4834Reviewed-by: Minux Ma <minux@golang.org>
Reviewed-by: Hyang-Ah Hana Kim <hyangah@gmail.com>
Run-TryBot: David Crawshaw <crawshaw@golang.org>

src/cmd/ld/lib.c

@@ -269,11 +269,13 @@ loadlib(void)
 	
 	tlsg = linklookup(ctxt, "runtime.tlsg", 0);
 	// For most ports, runtime.tlsg is a placeholder symbol for TLS
-	// relocation. However, the Android and Darwin ports need it to
-	// be a real variable. Instead of hard-coding which platforms
-	// need it to be a real variable, we set the type to STLSBSS only
-	// when the runtime has not declared its type already.
-	if(tlsg->type == 0)
+	// relocation. However, the Android and Darwin arm ports need it
+	// to be a real variable.
+	//
+	// TODO(crawshaw): android should require leaving the tlsg->type
+	// alone (as the runtime-provided SNOPTRBSS) just like darwin/arm.
+	// But some other part of the linker is expecting STLSBSS.
+	if (!(strcmp(goos, "darwin") == 0 && thearch.thechar == '5'))
 		tlsg->type = STLSBSS;
 	tlsg->size = thearch.ptrsize;
 	tlsg->hide = 1;