flux: add package (#2457)

packages/f/flux/xmake.lua

@@ -0,0 +1,25 @@
+package("flux")
+    set_kind("library", {headeronly = true})
+    set_homepage("https://tristanbrindle.com/flux/")
+    set_description("A C++20 library for sequence-orientated programming")
+    set_license("BSL-1.0")
+
+    add_urls("https://github.com/tcbrindle/flux.git")
+    add_versions("2023.08.17", "8434e8e0fd131cebc3aed0d845530335bf7fb5e1")
+
+    on_install(function (package)
+        os.cp("include", package:installdir())
+    end)
+
+    on_test(function (package)
+        assert(package:check_cxxsnippets({test = [[
+            #include <flux.hpp>
+            void test() {
+                constexpr auto result = flux::from(std::array{1, 2, 3, 4, 5})
+                         .filter(flux::pred::even)
+                         .map([](int i) { return i * 2; })
+                         .sum();
+                static_assert(result == 12);
+            }
+        ]]}, {configs = {languages = "c++20"}}))
+    end)