fix some packages tests for clang on Windows with msvc runtime (#3250)

packages/c/cxxopts/xmake.lua

@@ -35,6 +35,6 @@ package("cxxopts")
                   ("f,file", "File name", cxxopts::value<std::string>())
                   ("v,verbose", "Verbose output", cxxopts::value<bool>()->default_value("false"));
             }
-        ]]}, {configs = {languages = "c++11"}, includes = "cxxopts.hpp"}))
+        ]]}, {configs = {languages = "c++14"}, includes = "cxxopts.hpp"}))
     end)