add libtask package

packages/l/libtask/xmake.lua

@@ -0,0 +1,18 @@
+package("libtask")
+
+    set_homepage("https://swtch.com/libtask/")
+    set_description("a Coroutine Library for C and Unix")
+
+    set_urls("https://swtch.com/libtask.tar.gz")
+
+    add_versions("1.0", "4f484fbb29f8d016fa9f12a7c89abd9b0972cb677319369b076ec1558db7c327")
+
+    on_build("macosx", "linux", function (package)
+        os.vrun("make")
+    end)
+
+    on_install("macosx", "linux", function (package)
+        os.cp("*.h", package:installdir("include"))
+        os.cp("libtask.a", package:installdir("lib"))
+    end)
+