cmGeneratorTarget: Make GetConfigCommonSourceFiles Xcode-specific

The Xcode generator is the only place left that we do not support
per-config sources.  Make the corresponding helper Xcode-specific to
avoid any other new uses.

Source/cmGeneratorTarget.cxx

@@ -7039,7 +7039,7 @@ const cmLinkImplementation* cmGeneratorTarget::GetLinkImplementation(
   return &impl;
 }
 
-bool cmGeneratorTarget::GetConfigCommonSourceFiles(
+bool cmGeneratorTarget::GetConfigCommonSourceFilesForXcode(
   std::vector<cmSourceFile*>& files) const
 {
   std::vector<std::string> const& configs =

Source/cmGeneratorTarget.h

@@ -430,8 +430,9 @@ public:
 
   /** Get source files common to all configurations and diagnose cases
       with per-config sources.  Excludes sources added by a TARGET_OBJECTS
-      generator expression.  */
-  bool GetConfigCommonSourceFiles(std::vector<cmSourceFile*>& files) const;
+      generator expression.  Do not use outside the Xcode generator.  */
+  bool GetConfigCommonSourceFilesForXcode(
+    std::vector<cmSourceFile*>& files) const;
 
   bool HaveBuildTreeRPATH(const std::string& config) const;
 

Source/cmGlobalXCodeGenerator.cxx

@@ -1384,7 +1384,7 @@ bool cmGlobalXCodeGenerator::CreateXCodeTarget(
 
   // organize the sources
   std::vector<cmSourceFile*> commonSourceFiles;
-  if (!gtgt->GetConfigCommonSourceFiles(commonSourceFiles)) {
+  if (!gtgt->GetConfigCommonSourceFilesForXcode(commonSourceFiles)) {
     return false;
   }
 
@@ -1748,7 +1748,7 @@ void cmGlobalXCodeGenerator::CreateCustomCommands(
       this->CreateRunScriptBuildPhase("CMake PostBuild Rules", postbuild);
   } else {
     std::vector<cmSourceFile*> classes;
-    if (!gtgt->GetConfigCommonSourceFiles(classes)) {
+    if (!gtgt->GetConfigCommonSourceFilesForXcode(classes)) {
       return;
     }
     // add all the sources
@@ -1821,7 +1821,7 @@ void cmGlobalXCodeGenerator::CreateRunScriptBuildPhases(
   cmXCodeObject* buildPhases, cmGeneratorTarget const* gt)
 {
   std::vector<cmSourceFile*> sources;
-  if (!gt->GetConfigCommonSourceFiles(sources)) {
+  if (!gt->GetConfigCommonSourceFilesForXcode(sources)) {
     return;
   }
   auto& visited = this->CommandsVisited[gt];
@@ -2964,7 +2964,7 @@ cmXCodeObject* cmGlobalXCodeGenerator::CreateUtilityTarget(
   if (gtgt->GetType() != cmStateEnums::GLOBAL_TARGET &&
       gtgt->GetName() != CMAKE_CHECK_BUILD_SYSTEM_TARGET) {
     std::vector<cmSourceFile*> sources;
-    if (!gtgt->GetConfigCommonSourceFiles(sources)) {
+    if (!gtgt->GetConfigCommonSourceFilesForXcode(sources)) {
       return nullptr;
     }