emhash: add package (#4270)

packages/e/emhash/xmake.lua

@@ -0,0 +1,20 @@
+package("emhash")
+    set_kind("library", {headeronly = true})
+    set_homepage("https://github.com/ktprime/emhash")
+    set_description("Fast and memory efficient c++ flat hash map/set")
+    set_license("MIT")
+
+    add_urls("https://github.com/ktprime/emhash.git")
+    add_versions("2024.06.01", "3efa77ef32786a033b379071fe8af3dc705736ca")
+
+    on_install(function (package)
+        os.cp("*.hpp", package:installdir("include"))
+    end)
+
+    on_test(function (package)
+        assert(package:check_cxxsnippets({test = [[
+            void test() {
+                emhash5::HashMap<int, int> m1(4);
+            }
+        ]]}, {configs = {languages = "c++11"}, includes = "hash_table5.hpp"}))
+    end)