Use std::this_thread::yield() rather than sched_yield()

Summary: Because the former is standard and the latter doesn't exist on Windows.

Reviewed By: yfeldblum

Differential Revision: D9565344

fbshipit-source-id: c29c0623c87a20d4c16a29fec1a7311907c1c1cf

folly/logging/test/AsyncFileWriterTest.cpp

@@ -88,7 +88,7 @@ TEST(AsyncFileWriter, simpleMessages) {
     AsyncFileWriter writer{folly::File{tmpFile.fd(), false}};
     for (int n = 0; n < 10; ++n) {
       writer.writeMessage(folly::to<std::string>("message ", n, "\n"));
-      sched_yield();
+      std::this_thread::yield();
     }
   }
   tmpFile.close();
@@ -143,7 +143,7 @@ TEST(AsyncFileWriter, ioError) {
     AsyncFileWriter writer{folly::File{fds[1], true}};
     for (size_t n = 0; n < numMessages; ++n) {
       writer.writeMessage(folly::to<std::string>("message ", n, "\n"));
-      sched_yield();
+      std::this_thread::yield();
     }
   }