cmTarget: Remove obsolete member

Source/cmTarget.cxx

@@ -61,7 +61,6 @@ cmTarget::cmTarget()
   this->HaveInstallRule = false;
   this->DLLPlatform = false;
   this->IsAndroid = false;
-  this->IsApple = false;
   this->IsImportedTarget = false;
   this->BuildInterfaceIncludesAppended = false;
 }
@@ -98,9 +97,6 @@ void cmTarget::SetMakefile(cmMakefile* mf)
     strcmp(this->Makefile->GetSafeDefinition("CMAKE_SYSTEM_NAME"),
            "Android") == 0;
 
-  // Check whether we are targeting an Apple platform.
-  this->IsApple = this->Makefile->IsOn("APPLE");
-
   // Setup default property values.
   if (this->GetType() != cmState::INTERFACE_LIBRARY
       && this->GetType() != cmState::UTILITY)

Source/cmTarget.h

@@ -357,7 +357,6 @@ private:
   bool RecordDependencies;
   bool DLLPlatform;
   bool IsAndroid;
-  bool IsApple;
   bool IsImportedTarget;
   bool BuildInterfaceIncludesAppended;
 #if defined(_WIN32) && !defined(__CYGWIN__)