cmTarget: Remove unnecessary 'mutable' markup

Members of the cmTargetInternals structure do not need to be made
'mutable' even to cache data because there is no reason for the
internal methods to be 'const'.

Source/cmTarget.cxx

@@ -174,25 +174,25 @@ public:
   std::vector<TargetPropertyEntry*> SourceEntries;
   std::vector<cmValueWithOrigin> LinkImplementationPropertyEntries;
 
-  mutable std::map<std::string, std::vector<TargetPropertyEntry*> >
-                                CachedLinkInterfaceIncludeDirectoriesEntries;
-  mutable std::map<std::string, std::vector<TargetPropertyEntry*> >
-                                CachedLinkInterfaceCompileOptionsEntries;
-  mutable std::map<std::string, std::vector<TargetPropertyEntry*> >
-                                CachedLinkInterfaceCompileDefinitionsEntries;
-  mutable std::map<std::string, std::vector<TargetPropertyEntry*> >
-                                CachedLinkInterfaceSourcesEntries;
-  mutable std::map<std::string, std::vector<TargetPropertyEntry*> >
-                                CachedLinkInterfaceCompileFeaturesEntries;
-  mutable std::map<std::string, std::vector<cmTarget const*> >
-                                CachedLinkImplementationClosure;
-
-  mutable std::map<std::string, bool> CacheLinkInterfaceIncludeDirectoriesDone;
-  mutable std::map<std::string, bool> CacheLinkInterfaceCompileDefinitionsDone;
-  mutable std::map<std::string, bool> CacheLinkInterfaceCompileOptionsDone;
-  mutable std::map<std::string, bool> CacheLinkInterfaceSourcesDone;
-  mutable std::map<std::string, bool> CacheLinkInterfaceCompileFeaturesDone;
-  mutable std::map<std::string, bool> CacheLinkImplementationClosureDone;
+  std::map<std::string, std::vector<TargetPropertyEntry*> >
+                        CachedLinkInterfaceIncludeDirectoriesEntries;
+  std::map<std::string, std::vector<TargetPropertyEntry*> >
+                        CachedLinkInterfaceCompileOptionsEntries;
+  std::map<std::string, std::vector<TargetPropertyEntry*> >
+                        CachedLinkInterfaceCompileDefinitionsEntries;
+  std::map<std::string, std::vector<TargetPropertyEntry*> >
+                        CachedLinkInterfaceSourcesEntries;
+  std::map<std::string, std::vector<TargetPropertyEntry*> >
+                        CachedLinkInterfaceCompileFeaturesEntries;
+  std::map<std::string, std::vector<cmTarget const*> >
+                        CachedLinkImplementationClosure;
+
+  std::map<std::string, bool> CacheLinkInterfaceIncludeDirectoriesDone;
+  std::map<std::string, bool> CacheLinkInterfaceCompileDefinitionsDone;
+  std::map<std::string, bool> CacheLinkInterfaceCompileOptionsDone;
+  std::map<std::string, bool> CacheLinkInterfaceSourcesDone;
+  std::map<std::string, bool> CacheLinkInterfaceCompileFeaturesDone;
+  std::map<std::string, bool> CacheLinkImplementationClosureDone;
 };
 
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