Annotate iOS specific components

Use `#if TARGET_OS_IOS || TARGET_OS_MACCATALYST` to annotate iOS specific components.
1. EMM and MDM related classes.
 EMM/MDM: Enterprise Mobility Management or Mobile Device
 Management only apply to iOS.
2. GIDSignInButton.
 It is created based on UIKit.

Author: Alex-4-Git

GoogleSignIn/Sources/GIDEMMErrorHandler.h

@@ -13,6 +13,9 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
+#include <TargetConditionals.h>
+
+#if TARGET_OS_IOS || TARGET_OS_MACCATALYST
 
 #import <Foundation/Foundation.h>
 
@@ -35,3 +38,5 @@ NS_ASSUME_NONNULL_BEGIN
 @end
 
 NS_ASSUME_NONNULL_END
+
+#endif

GoogleSignIn/Sources/GIDEMMErrorHandler.m

@@ -11,6 +11,9 @@
 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 // See the License for the specific language governing permissions and
 // limitations under the License.
+#include <TargetConditionals.h>
+
+#if TARGET_OS_IOS || TARGET_OS_MACCATALYST
 
 #import "GoogleSignIn/Sources/GIDEMMErrorHandler.h"
 
@@ -283,3 +286,5 @@ - (NSString *)cancelString {
 @end
 
 NS_ASSUME_NONNULL_END
+
+#endif

GoogleSignIn/Sources/GIDMDMPasscodeCache.h

@@ -13,6 +13,9 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
+#include <TargetConditionals.h>
+
+#if TARGET_OS_IOS || TARGET_OS_MACCATALYST
 
 #import <Foundation/Foundation.h>
 
@@ -39,3 +42,5 @@ NS_ASSUME_NONNULL_BEGIN
 @end
 
 NS_ASSUME_NONNULL_END
+
+#endif

GoogleSignIn/Sources/GIDMDMPasscodeCache.m

@@ -11,6 +11,9 @@
 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 // See the License for the specific language governing permissions and
 // limitations under the License.
+#include <TargetConditionals.h>
+
+#if TARGET_OS_IOS || TARGET_OS_MACCATALYST
 
 #import "GoogleSignIn/Sources/GIDMDMPasscodeCache.h"
 
@@ -294,3 +297,5 @@ - (NSString *)info {
 @end
 
 NS_ASSUME_NONNULL_END
+
+#endif

GoogleSignIn/Sources/GIDMDMPasscodeState.h

@@ -13,6 +13,9 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
+#include <TargetConditionals.h>
+
+#if TARGET_OS_IOS || TARGET_OS_MACCATALYST
 
 #import <Foundation/Foundation.h>
 
@@ -48,3 +51,4 @@ NS_ASSUME_NONNULL_BEGIN
 
 NS_ASSUME_NONNULL_END
 
+#endif

GoogleSignIn/Sources/GIDMDMPasscodeState.m

@@ -11,6 +11,9 @@
 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 // See the License for the specific language governing permissions and
 // limitations under the License.
+#include <TargetConditionals.h>
+
+#if TARGET_OS_IOS || TARGET_OS_MACCATALYST
 
 #import "GoogleSignIn/Sources/GIDMDMPasscodeState.h"
 
@@ -48,3 +51,5 @@ + (instancetype)passcodeState {
 @end
 
 NS_ASSUME_NONNULL_END
+
+#endif

GoogleSignIn/Sources/GIDMDMPasscodeState_Private.h

@@ -13,6 +13,9 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
+#include <TargetConditionals.h>
+
+#if TARGET_OS_IOS || TARGET_OS_MACCATALYST
 
 #import <Foundation/Foundation.h>
 
@@ -33,3 +36,5 @@ NS_ASSUME_NONNULL_BEGIN
 @end
 
 NS_ASSUME_NONNULL_END
+
+#endif

GoogleSignIn/Sources/GIDSignInButton.m

@@ -11,6 +11,9 @@
 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 // See the License for the specific language governing permissions and
 // limitations under the License.
+#include <TargetConditionals.h>
+
+#if TARGET_OS_IOS || TARGET_OS_MACCATALYST
 
 #import "GoogleSignIn/Sources/Public/GoogleSignIn/GIDSignInButton.h"
 
@@ -639,3 +642,5 @@ - (UIImage *)gid_imageWithBlendMode:(CGBlendMode)blendMode color:(UIColor *)colo
 @end
 
 NS_ASSUME_NONNULL_END
+
+#endif

GoogleSignIn/Sources/GIDSignInCallbackSchemes.m

@@ -14,8 +14,6 @@
 
 #import "GoogleSignIn/Sources/GIDSignInCallbackSchemes.h"
 
-#import <UIKit/UIKit.h>
-
 NS_ASSUME_NONNULL_BEGIN
 
 @implementation GIDSignInCallbackSchemes {

GoogleSignIn/Sources/Public/GoogleSignIn/GIDSignInButton.h

@@ -13,6 +13,9 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
+#include <TargetConditionals.h>
+
+#if TARGET_OS_IOS || TARGET_OS_MACCATALYST
 
 #import <UIKit/UIKit.h>
 
@@ -61,3 +64,5 @@ typedef NS_ENUM(NSInteger, GIDSignInButtonColorScheme) {
 @end
 
 NS_ASSUME_NONNULL_END
+
+#endif