Make C10_MOBILE consistent with how feature macros are usually used (#17481)

Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/17481

Usually, feature macros are either defined or undefined and checked accordingly.
C10_MOBILE was a weird special case that was always defined but either defined to 1 or to 0.

This caused a lot of confusion for me when trying to disable something from mobile build and it also disabled it
from the server build (because I was using ifdef). Also, I found a place in the existing code base that made
that wrong assumption and used the macro wrongly, see https://fburl.com/y4icohts

Reviewed By: dzhulgakov

Differential Revision: D14214825

fbshipit-source-id: f3a155b6d43d334e8839e2b2e3c40ed2c773eab6

1 files changed, 3 insertions, 3 deletions

diff --git a/modules/observers/perf_observer.cc b/modules/observers/perf_observer.cc
index ea5d22c254..2de1ce6511 100644
--- a/modules/observers/perf_observer.cc
+++ b/modules/observers/perf_observer.cc
@@ -1,6 +1,6 @@
 #include "observers/perf_observer.h"
 #include "observers/observer_config.h"
-#if !C10_MOBILE
+#ifndef C10_MOBILE
 #include "caffe2/core/flags.h"
 #include "observers/net_observer_reporter_print.h"
 #endif
@@ -10,7 +10,7 @@
 #include "caffe2/core/init.h"
 #include "caffe2/core/operator.h"
 
-#if !C10_MOBILE
+#ifndef C10_MOBILE
 C10_DEFINE_int64(
     aiBench_netInitSampleRate,
     0,
@@ -45,7 +45,7 @@ bool registerGlobalPerfNetObserverCreator(int* /*pargc*/, char*** /*pargv*/) {
     return caffe2::make_unique<PerfNetObserver>(subject);
   });
 
-#if !C10_MOBILE
+#if !defined(C10_MOBILE)
   // for aibench usage
   caffe2::ObserverConfig::setReporter(
       caffe2::make_unique<caffe2::NetObserverReporterPrint>());