Add mapbox_variant (#1138)

packages/m/mapbox_variant/xmake.lua

@@ -0,0 +1,35 @@
+package("mapbox_variant")
+
+    set_kind("library", {headeronly = true})
+    set_homepage("https://github.com/mapbox/variant")
+    set_description("C++11/C++14 Variant")
+    set_license("BSD")
+
+    set_urls("https://github.com/mapbox/variant/archive/refs/tags/$(version).tar.gz",
+             "https://github.com/mapbox/variant.git")
+
+    add_versions("v1.2.0", "7059f4420d504c4bc96f8a462a0f6d029c5be914ba55cc030a0a773366dd7bc8")
+
+    on_install(function (package)
+        os.cp("include/mapbox", package:installdir("include"))
+    end)
+
+    on_test(function (package)
+        assert(package:check_cxxsnippets({test = [[
+            struct Result {};
+            struct Error
+            {
+                unsigned int code;
+            };
+
+            using Response = mapbox::util::variant<Result, Error>;
+          
+            void test()
+            {
+                Response ret = Result {};
+                ret.match([] (const Result& r) { },
+                          [] (const Error& e)  { });
+
+            }
+        ]]}, {configs = {languages = "c++14"}, includes = { "mapbox/variant.hpp"} }))
+    end)