clang-tidy: Resolve performance-unnecessary-value-param diagnostics

Fix diagnostics that appear on macOS with clang-tidy-8.  Suppress cases
where we intentionally take an argument by value to let the caller
choose whether to copy or move.

Source/cmGlobalXCodeGenerator.cxx

@@ -1433,7 +1433,7 @@ cmXCodeObject* cmGlobalXCodeGenerator::CreateBuildPhase(
 void cmGlobalXCodeGenerator::CreateCustomCommands(
   cmXCodeObject* buildPhases, cmXCodeObject* sourceBuildPhase,
   cmXCodeObject* headerBuildPhase, cmXCodeObject* resourceBuildPhase,
-  std::vector<cmXCodeObject*> contentBuildPhases,
+  std::vector<cmXCodeObject*> const& contentBuildPhases,
   cmXCodeObject* frameworkBuildPhase, cmGeneratorTarget* gtgt)
 {
   std::vector<cmCustomCommand> const& prebuild = gtgt->GetPreBuildCommands();

Source/cmGlobalXCodeGenerator.h

@@ -122,13 +122,11 @@ private:
   std::string RelativeToSource(const std::string& p);
   std::string RelativeToBinary(const std::string& p);
   std::string ConvertToRelativeForMake(std::string const& p);
-  void CreateCustomCommands(cmXCodeObject* buildPhases,
-                            cmXCodeObject* sourceBuildPhase,
-                            cmXCodeObject* headerBuildPhase,
-                            cmXCodeObject* resourceBuildPhase,
-                            std::vector<cmXCodeObject*> contentBuildPhases,
-                            cmXCodeObject* frameworkBuildPhase,
-                            cmGeneratorTarget* gtgt);
+  void CreateCustomCommands(
+    cmXCodeObject* buildPhases, cmXCodeObject* sourceBuildPhase,
+    cmXCodeObject* headerBuildPhase, cmXCodeObject* resourceBuildPhase,
+    std::vector<cmXCodeObject*> const& contentBuildPhases,
+    cmXCodeObject* frameworkBuildPhase, cmGeneratorTarget* gtgt);
 
   std::string ComputeInfoPListLocation(cmGeneratorTarget* target);
 

Source/cmListFileCache.cxx

@@ -326,6 +326,7 @@ cmListFileBacktrace::cmListFileBacktrace(cmStateSnapshot const& snapshot)
 {
 }
 
+/* NOLINTNEXTLINE(performance-unnecessary-value-param) */
 cmListFileBacktrace::cmListFileBacktrace(std::shared_ptr<Entry const> parent,
                                          cmListFileContext const& lfc)
   : TopEntry(std::make_shared<Entry const>(std::move(parent), lfc))

Source/cmVariableWatchCommand.cxx

@@ -91,6 +91,7 @@ static void deleteVariableWatchCallbackData(void* client_data)
 class FinalAction
 {
 public:
+  /* NOLINTNEXTLINE(performance-unnecessary-value-param) */
   FinalAction(cmMakefile* makefile, std::string variable)
     : Action(std::make_shared<Impl>(makefile, std::move(variable)))
   {