Move signal_blocker to platform and use it by default in TEMP_FAILURE_RETRY.

runtime/bin/eventhandler_macos.h

Index: runtime/bin/eventhandler_macos.h
diff --git a/runtime/bin/eventhandler_macos.h b/runtime/bin/eventhandler_macos.h
index 70a103c87ee0297b79df5115e08d80213150cf3e..18e463b77d88f2d23f2a5e61265b40cbd4ea0b1c 100644
--- a/runtime/bin/eventhandler_macos.h
+++ b/runtime/bin/eventhandler_macos.h
@@ -9,11 +9,13 @@
 #error Do not include eventhandler_macos.h directly; use eventhandler.h instead.
 #endif
 
-#include <unistd.h>
+#include <errno.h>
 #include <sys/event.h>  // NOLINT
 #include <sys/socket.h>
+#include <unistd.h>
 
 #include "platform/hashmap.h"
+#include "platform/signal_blocker.h"
 
 
 namespace dart {
@@ -44,7 +46,7 @@ class SocketData {
   void Close() {
     port_ = 0;
     mask_ = 0;
-    close(fd_);
+    VOID_TEMP_FAILURE_RETRY(close(fd_));
     fd_ = -1;
   }