fixed some Variable copied when it could be moved Coverity warnings

lib/analyzerinfo.cpp

@@ -142,7 +142,7 @@ std::string AnalyzerInformation::getAnalyzerInfoFile(const std::string &buildDir
         filename = sourcefile;
     else
         filename = sourcefile.substr(pos + 1);
-    return Path::join(buildDir, filename) + ".analyzerinfo";
+    return Path::join(buildDir, std::move(filename)) + ".analyzerinfo";
 }
 
 bool AnalyzerInformation::analyzeFile(const std::string &buildDir, const std::string &sourcefile, const std::string &cfg, int fileIndex, std::size_t hash, std::list<ErrorMessage> &errors)

lib/checkother.cpp

@@ -4442,7 +4442,7 @@ static std::vector<Union> parseUnions(const SymbolDatabase &symbolDatabase,
         for (const Variable &var : scope.varlist) {
             u.members.push_back(parseUnionMember(var, settings));
         }
-        unions.push_back(u);
+        unions.push_back(std::move(u));
     }
 
     return unions;

lib/platform.cpp

@@ -180,7 +180,7 @@ bool Platform::loadFromFile(const std::vector<std::string>& paths, const std::st
     std::vector<std::string> filenames;
     if (is_abs_path)
     {
-        filenames.push_back(fullfilename);
+        filenames.push_back(std::move(fullfilename));
     }
     else {
         // TODO: drop duplicated paths