[dev.cc] runtime: print to stderr as well as android logd

Restores stack traces in the android/arm builder.

Change-Id: If637aa2ed6f8886126b77cf9cc8a0535ec7c4369
Reviewed-on: https://go-review.googlesource.com/5453
Reviewed-by: Hyang-Ah Hana Kim <hyangah@gmail.com>

src/runtime/print1_write_android.go

@@ -45,6 +45,9 @@ func writeErr(b []byte) {
 		}
 	}
 
+	// Write to stderr for command-line programs.
+	write(2, unsafe.Pointer(&b[0]), int32(len(b)))
+
 	// Log format: "<header>\x00<message m bytes>\x00"
 	//
 	// <header>