create flecs package (#1271)

packages/f/flecs/xmake.lua

@@ -0,0 +1,26 @@
+package("flecs")
+
+    set_homepage("https://github.com/SanderMertens/flecs")
+    set_description("A fast entity component system (ECS) for C & C++")
+    set_license("MIT")
+
+    add_urls("https://github.com/SanderMertens/flecs.git")
+    add_versions("v3.0.1-alpha", "9d9a2fbea143a7237ae7020748180d896839e328a5d34bb769808abf904fcbf0")
+    add_versions("v2.4.8", "8b24c11b0513ee6ad3904165ed0927d59cbff2acc9bce0f8f989f493891d7deb")
+
+    add_deps("cmake")
+
+    on_install("windows", "macosx", "linux", function (package)
+        local configs = {}
+        table.insert(configs, "-DCMAKE_BUILD_TYPE=" .. (package:debug() and "Debug" or "Release"))
+        table.insert(configs, "-DBUILD_SHARED_LIBS=" .. (package:config("shared") and "ON" or "OFF"))
+        import("package.tools.cmake").install(package, configs)
+    end)
+
+    on_test(function (package)
+        assert(package:check_cxxsnippets({test = [[
+            void test() {
+				flecs::world ecs;
+            }
+        ]]}, {configs = {languages = "c++11"}, includes = "flecs.h"}))
+    end)