add frozenca-btree (#1430)

* add btree

* Update and rename packages/b/btree/xmake.lua to packages/f/frozenca-btree/xmake.lua

* Update xmake.lua

* Update xmake.lua

packages/f/frozenca-btree/xmake.lua

@@ -0,0 +1,30 @@
+package("frozenca-btree")
+    set_kind("library", {headeronly = true})
+    set_homepage("https://github.com/frozenca/BTree")
+    set_description("A general-purpose high-performance lightweight STL-like modern C++ B-Tree")
+    set_license("Apache-2.0")
+
+    add_urls("https://github.com/frozenca/BTree.git")
+    add_versions("2022.08.02", "c2318e18194018f092c3e30ddd7385a50216b3a0")
+
+    on_install("linux", "windows", function (package)
+        os.cp("*.h", package:installdir("include"))
+    end)
+
+    on_test(function(package)
+        assert(package:check_cxxsnippets({
+            test = [[
+                #include "fc_btree.h"
+                #include <iostream>
+                #include <string>
+
+                static void test() {
+                    namespace fc = frozenca;
+                    fc::BTreeSet<int> btree;
+
+                    btree.insert(3);
+                    btree.insert(4);
+                }
+            ]]
+        }, {configs = {languages = "c++20", cxflags = "-fconcepts"}}))
+    end)