cmLocalGenerator: add an override for CMakeFiles-using paths

Visual Studio doesn't use a `CMakeFiles` subdirectory for its support
directories. However, some codepaths expect to use paths which are
always under `CMakeFiles`. Add a mechanism to keep the path for such
files.

Source/cmGeneratorTarget.cxx

@@ -2851,7 +2851,7 @@ std::string cmGeneratorTarget::GetPchHeader(std::string const& config,
       { "OBJCXX", ".objcxx.hxx" }
     };
 
-    filename = generatorTarget->GetSupportDirectory();
+    filename = generatorTarget->GetCMFSupportDirectory();
 
     if (this->GetGlobalGenerator()->IsMultiConfig()) {
       filename = cmStrCat(filename, '/', config);
@@ -2944,7 +2944,8 @@ std::string cmGeneratorTarget::GetPchSource(std::string const& config,
         this->GetGlobalGenerator()->FindGeneratorTarget(*pchReuseFrom);
     }
 
-    filename = cmStrCat(generatorTarget->GetSupportDirectory(), "/cmake_pch");
+    filename =
+      cmStrCat(generatorTarget->GetCMFSupportDirectory(), "/cmake_pch");
 
     // For GCC the source extension will be transformed into .h[xx].gch
     if (!this->Makefile->IsOn("CMAKE_LINK_PCH")) {
@@ -5222,6 +5223,17 @@ std::string cmGeneratorTarget::GetSupportDirectory() const
                   lg->GetTargetDirectory(this));
 }
 
+std::string cmGeneratorTarget::GetCMFSupportDirectory() const
+{
+  cmLocalGenerator* lg = this->GetLocalGenerator();
+  if (!lg->AlwaysUsesCMFPaths()) {
+    return cmStrCat(lg->GetCurrentBinaryDirectory(), "/CMakeFiles/",
+                    lg->GetTargetDirectory(this));
+  }
+  return cmStrCat(lg->GetObjectOutputRoot(), '/',
+                  lg->GetTargetDirectory(this));
+}
+
 bool cmGeneratorTarget::IsLinkable() const
 {
   return (this->GetType() == cmStateEnums::STATIC_LIBRARY ||

Source/cmGeneratorTarget.h

@@ -935,6 +935,7 @@ public:
 
   /** Get a build-tree directory in which to place target support files.  */
   std::string GetSupportDirectory() const;
+  std::string GetCMFSupportDirectory() const;
 
   /** Return whether this target may be used to link another target.  */
   bool IsLinkable() const;

Source/cmGlobalGenerator.cxx

@@ -3636,7 +3636,7 @@ void cmGlobalGenerator::WriteSummary()
         continue;
       }
       this->WriteSummary(tgt.get());
-      fout << tgt->GetSupportDirectory() << '\n';
+      fout << tgt->GetCMFSupportDirectory() << '\n';
     }
   }
 }
@@ -3644,7 +3644,7 @@ void cmGlobalGenerator::WriteSummary()
 void cmGlobalGenerator::WriteSummary(cmGeneratorTarget* target)
 {
   // Place the labels file in a per-target support directory.
-  std::string dir = target->GetSupportDirectory();
+  std::string dir = target->GetCMFSupportDirectory();
   std::string file = cmStrCat(dir, "/Labels.txt");
   std::string json_file = cmStrCat(dir, "/Labels.json");
 

Source/cmInstallCxxModuleBmiGenerator.cxx

@@ -51,7 +51,7 @@ std::string cmInstallCxxModuleBmiGenerator::GetScriptLocation(
   if (config.empty()) {
     config_name = "noconfig";
   }
-  return cmStrCat(this->Target->GetSupportDirectory(),
+  return cmStrCat(this->Target->GetCMFSupportDirectory(),
                   "/install-cxx-module-bmi-", config_name, ".cmake");
 }
 

Source/cmLocalGenerator.cxx

@@ -3323,7 +3323,7 @@ void cmLocalGenerator::AddUnityBuild(cmGeneratorTarget* target)
   }
 
   std::string filename_base =
-    cmStrCat(target->GetSupportDirectory(), "/Unity/");
+    cmStrCat(target->GetCMFSupportDirectory(), "/Unity/");
 
   cmValue batchSizeString = target->GetProperty("UNITY_BUILD_BATCH_SIZE");
   size_t const unityBatchSize = batchSizeString
@@ -4291,6 +4291,11 @@ std::string cmLocalGenerator::GetObjectOutputRoot() const
   return cmStrCat(this->GetCurrentBinaryDirectory(), "/CMakeFiles");
 }
 
+bool cmLocalGenerator::AlwaysUsesCMFPaths() const
+{
+  return true;
+}
+
 std::string cmLocalGenerator::GetSourceFileLanguage(cmSourceFile const& source)
 {
   return source.GetLanguage();

Source/cmLocalGenerator.h

@@ -439,6 +439,7 @@ public:
   std::string const& GetCurrentSourceDirectory() const;
 
   virtual std::string GetObjectOutputRoot() const;
+  virtual bool AlwaysUsesCMFPaths() const;
 
   /**
    * Generate a macOS application bundle Info.plist file.

Source/cmLocalVisualStudioGenerator.cxx

@@ -89,6 +89,11 @@ std::string cmLocalVisualStudioGenerator::GetObjectOutputRoot() const
   return this->GetCurrentBinaryDirectory();
 }
 
+bool cmLocalVisualStudioGenerator::AlwaysUsesCMFPaths() const
+{
+  return false;
+}
+
 std::unique_ptr<cmCustomCommand>
 cmLocalVisualStudioGenerator::MaybeCreateImplibDir(cmGeneratorTarget* target,
                                                    std::string const& config,

Source/cmLocalVisualStudioGenerator.h

@@ -52,6 +52,7 @@ public:
     cmGeneratorTarget const* = nullptr) override;
 
   std::string GetObjectOutputRoot() const override;
+  bool AlwaysUsesCMFPaths() const override;
 
 protected:
   virtual char const* ReportErrorLabel() const;