[half] add package (#2480)

* [half] add package

* [half] tweaks

packages/h/half/xmake.lua

@@ -0,0 +1,21 @@
+package("half")
+    set_kind("library", {headeronly = true})
+    set_homepage("https://half.sourceforge.net")
+    set_description("C++ library for half precision floating point arithmetics")
+    set_license("MIT")
+
+    add_urls("https://downloads.sourceforge.net/project/half/half/$(version)/half-$(version).zip")
+    add_versions("2.2.0", "1d1d9e482fb95fcd7cab0953a4bd35e00b86578f11cb6939a067811a055a563b")
+
+    on_install("windows", "linux", "macosx", "iphoneos", "android", "bsd", function (package)
+        os.cp("include", package:installdir())
+    end)
+
+    on_test(function (package)
+        assert(package:check_cxxsnippets({test = [[
+            void test() {
+                half_float::half a{ 3.1415926f };
+                float b{ a };
+            }
+        ]]}, {configs = {languages = "c++11"}, includes = "half.hpp"}))
+    end)