Compile ios helpers on mac as well.

BUG=webrtc:5582

Review-Url: https://codereview.webrtc.org/2586433002
Cr-Commit-Position: refs/heads/master@{#16604}
diff --git a/webrtc/sdk/BUILD.gn b/webrtc/sdk/BUILD.gn
index 3e44f9b..68d7f5f 100644
--- a/webrtc/sdk/BUILD.gn
+++ b/webrtc/sdk/BUILD.gn
@@ -47,6 +47,8 @@
       "objc/Framework/Classes/RTCMetricsSampleInfo.mm",
       "objc/Framework/Classes/RTCSSLAdapter.mm",
       "objc/Framework/Classes/RTCTracing.mm",
+      "objc/Framework/Classes/helpers.h",
+      "objc/Framework/Classes/helpers.mm",
       "objc/Framework/Headers/WebRTC/RTCDispatcher.h",
       "objc/Framework/Headers/WebRTC/RTCFieldTrials.h",
       "objc/Framework/Headers/WebRTC/RTCLogging.h",
@@ -62,8 +64,6 @@
         "objc/Framework/Classes/RTCUIApplication.h",
         "objc/Framework/Classes/RTCUIApplication.mm",
         "objc/Framework/Classes/UIDevice+RTCDevice.mm",
-        "objc/Framework/Classes/helpers.h",
-        "objc/Framework/Classes/helpers.mm",
         "objc/Framework/Headers/WebRTC/RTCCameraPreviewView.h",
         "objc/Framework/Headers/WebRTC/UIDevice+RTCDevice.h",
       ]
diff --git a/webrtc/sdk/objc/Framework/Classes/helpers.mm b/webrtc/sdk/objc/Framework/Classes/helpers.mm
index ef0e280..c0e5f1e 100644
--- a/webrtc/sdk/objc/Framework/Classes/helpers.mm
+++ b/webrtc/sdk/objc/Framework/Classes/helpers.mm
@@ -8,12 +8,13 @@
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
-#if defined(WEBRTC_IOS)
 
 #import <AVFoundation/AVFoundation.h>
 #import <Foundation/Foundation.h>
 #import <sys/sysctl.h>
+#if defined(WEBRTC_IOS)
 #import <UIKit/UIKit.h>
+#endif
 
 #include <memory>
 
@@ -24,9 +25,11 @@
 namespace webrtc {
 namespace ios {
 
+#if defined(WEBRTC_IOS)
 bool isOperatingSystemAtLeastVersion(double version) {
   return GetSystemVersion() >= version;
 }
+#endif
 
 NSString* NSStringFromStdString(const std::string& stdString) {
   // std::string may contain null termination character so we construct
@@ -61,6 +64,7 @@
   return StdStringFromNSString(name);
 }
 
+#if defined(WEBRTC_IOS)
 std::string GetAudioSessionCategory() {
   NSString* category = [[AVAudioSession sharedInstance] category];
   return StdStringFromNSString(category);
@@ -89,6 +93,7 @@
   NSString* deviceModel = [[UIDevice currentDevice] model];
   return StdStringFromNSString(deviceModel);
 }
+#endif
 
 std::string GetDeviceName() {
   size_t size;
@@ -134,4 +139,3 @@
 }  // namespace ios
 }  // namespace webrtc
 
-#endif  // defined(WEBRTC_IOS)