Enable -Wformat in linux, android, chromeos, cast builds.

tools/android/file_poller/file_poller.cc

Index: tools/android/file_poller/file_poller.cc
diff --git a/tools/android/file_poller/file_poller.cc b/tools/android/file_poller/file_poller.cc
index f7b6d584c23a2defb003ff50610961c45939462a..448e229aaf4314970bdfe750438698e77b615dde 100644
--- a/tools/android/file_poller/file_poller.cc
+++ b/tools/android/file_poller/file_poller.cc
@@ -88,7 +88,7 @@ void acquire_sample(int fd, const Context& context) {
   struct timeval tv;
   gettimeofday(&tv, NULL);
   char buffer[1024];
-  int n = snprintf(buffer, sizeof(buffer), "%d.%06d ", tv.tv_sec, tv.tv_usec);
+  int n = snprintf(buffer, sizeof(buffer), "%ld.%06ld ", tv.tv_sec, tv.tv_usec);
   safe_write(fd, buffer, n);
 
   for (int i = 0; i < context.nb_files; ++i)