libbinder: separate OS-specific code from Utils.cpp

Separate the OS-specific functions setNonBlocking and
getRandomBytes from Utils.cpp into a separate OS-specific
OS.cpp file that other operating systems can override at
build time.

Bug: 224644083
Test: build Trusty
Change-Id: I2703fb81d4370b5f6264556ae57fdddb0573971a
diff --git a/libs/binder/OS.h b/libs/binder/OS.h
new file mode 100644
index 0000000..e802e9c
--- /dev/null
+++ b/libs/binder/OS.h
@@ -0,0 +1,31 @@
+/*
+ * Copyright (C) 2022 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+#pragma once
+
+#include <stddef.h>
+#include <cstdint>
+
+#include <android-base/result.h>
+#include <android-base/unique_fd.h>
+#include <utils/Errors.h>
+
+namespace android {
+
+android::base::Result<void> setNonBlocking(android::base::borrowed_fd fd);
+
+status_t getRandomBytes(uint8_t* data, size_t size);
+
+} // namespace android