Export: Use existing IsDLLPlatform porcelain

Source/cmExportBuildFileGenerator.cxx

@@ -213,12 +213,8 @@ cmExportBuildFileGenerator
   properties[prop] = value;
   }
 
-  // Check whether this is a DLL platform.
-  bool dll_platform =
-    (mf->IsOn("WIN32") || mf->IsOn("CYGWIN") || mf->IsOn("MINGW"));
-
   // Add the import library for windows DLLs.
-  if(dll_platform &&
+  if(target->IsDLLPlatform() &&
      (target->GetType() == cmState::SHARED_LIBRARY ||
       target->IsExecutableWithExports()) &&
      mf->GetDefinition("CMAKE_IMPORT_LIBRARY_SUFFIX"))

Source/cmExportFileGenerator.cxx

@@ -879,10 +879,7 @@ cmExportFileGenerator
   if(target->GetType() == cmState::SHARED_LIBRARY ||
      target->GetType() == cmState::MODULE_LIBRARY)
     {
-    // Check whether this is a DLL platform.
-    bool dll_platform =
-      (mf->IsOn("WIN32") || mf->IsOn("CYGWIN") || mf->IsOn("MINGW"));
-    if(!dll_platform)
+    if(!target->IsDLLPlatform())
       {
       std::string prop;
       std::string value;