ui/app: (android) set close-on-exit flag on dup'ed log file descriptors

The file descriptors are probably overwritten on exec anyway, but at
least our intent is clear.

Signed-off-by: Elias Naur <mail@eliasnaur.com>

ui/app/log_android.go

@@ -31,7 +31,7 @@ func logFd(prio C.int, fd uintptr) {
 	if err != nil {
 		panic(err)
 	}
-	if err := syscall.Dup3(int(w.Fd()), int(fd), 0); err != nil {
+	if err := syscall.Dup3(int(w.Fd()), int(fd), syscall.O_CLOEXEC); err != nil {
 		panic(err)
 	}
 	go func() {