style(3p/nix): Reformat project in Google C++ style

Reformatted with:

    fd . -e hh -e cc | xargs clang-format -i

third_party/nix/src/libutil/monitor-fd.hh

@@ -1,58 +1,52 @@
 #pragma once
 
-#include <thread>
-#include <atomic>
-
-#include <cstdlib>
 #include <poll.h>
+#include <signal.h>
 #include <sys/types.h>
 #include <unistd.h>
-#include <signal.h>
+#include <atomic>
+#include <cstdlib>
+#include <thread>
 
 namespace nix {
 
+class MonitorFdHup {
+ private:
+  std::thread thread;
 
-class MonitorFdHup
-{
-private:
-    std::thread thread;
+ public:
+  MonitorFdHup(int fd) {
+    thread = std::thread([fd]() {
+      while (true) {
+        /* Wait indefinitely until a POLLHUP occurs. */
+        struct pollfd fds[1];
+        fds[0].fd = fd;
+        /* This shouldn't be necessary, but macOS doesn't seem to
+           like a zeroed out events field.
+           See rdar://37537852.
+        */
+        fds[0].events = POLLHUP;
+        auto count = poll(fds, 1, -1);
+        if (count == -1) abort();  // can't happen
+        /* This shouldn't happen, but can on macOS due to a bug.
+           See rdar://37550628.
 
-public:
-    MonitorFdHup(int fd)
-    {
-        thread = std::thread([fd]() {
-            while (true) {
-              /* Wait indefinitely until a POLLHUP occurs. */
-              struct pollfd fds[1];
-              fds[0].fd = fd;
-              /* This shouldn't be necessary, but macOS doesn't seem to
-                 like a zeroed out events field.
-                 See rdar://37537852.
-              */
-              fds[0].events = POLLHUP;
-              auto count = poll(fds, 1, -1);
-              if (count == -1) abort(); // can't happen
-              /* This shouldn't happen, but can on macOS due to a bug.
-                 See rdar://37550628.
+           This may eventually need a delay or further
+           coordination with the main thread if spinning proves
+           too harmful.
+         */
+        if (count == 0) continue;
+        assert(fds[0].revents & POLLHUP);
+        triggerInterrupt();
+        break;
+      }
+    });
+  };
 
-                 This may eventually need a delay or further
-                 coordination with the main thread if spinning proves
-                 too harmful.
-               */
-              if (count == 0) continue;
-              assert(fds[0].revents & POLLHUP);
-              triggerInterrupt();
-              break;
-            }
-        });
-    };
-
-    ~MonitorFdHup()
-    {
-        pthread_cancel(thread.native_handle());
-        thread.join();
-    }
+  ~MonitorFdHup() {
+    pthread_cancel(thread.native_handle());
+    thread.join();
+  }
 };
 
-
-}
+}  // namespace nix