add flags (#2914)

* add flags

* rename flags

---------

Co-authored-by: Your Name <you@example.com>

packages/s/sailormoon_flags/xmake.lua

@@ -0,0 +1,23 @@
+package("sailormoon_flags")
+    set_kind("library", {headeronly = true})
+    set_homepage("https://github.com/sailormoon/flags")
+    set_description("Simple, extensible, header-only C++17 argument parser released into the public domain.")
+    set_license("MIT")
+
+    add_urls("https://github.com/sailormoon/flags/archive/refs/tags/v$(version).tar.gz")
+    add_versions("1.1", "f6626c97ba7a45c473557db2e4b68df4d9cda18a8a97c89a5d8d4e5c53dde904")
+
+    on_install(function (package)
+        os.cp("include", package:installdir())
+    end)
+
+    on_test(function (package)
+        assert(package:check_cxxsnippets({test = [[
+            #include "flags.h"
+            void test() {
+                int argc = 2;
+                char **argv = NULL;
+                const flags::args args(argc, argv);
+            }
+        ]]}, {configs = {languages = "c++17"}}))
+    end)