Import source to librtti

Summary:

- Import initial source

Test Plan:
NA

flake.nix

@@ -0,0 +1,42 @@
+{
+  description = "Flake for librtti";
+
+  inputs = {
+    nixpkgs.url = "github:nixos/nixpkgs?ref=nixos-unstable";
+    flake-utils.url = "github:numtide/flake-utils";
+    xbuild.url = "github:shen390s/my-nix-channel?ref=master";
+  };
+
+  outputs =
+    {
+      self,
+      nixpkgs,
+      flake-utils,
+      xbuild,
+    }:
+    let
+      supportedSystems = [ "x86_64-linux" ];
+    in
+    flake-utils.lib.eachSystem supportedSystems (
+      system:
+      let
+        mypkgs = xbuild.packages.${system};
+        overlays = [
+          (final: prev: mypkgs // prev)
+        ];
+        pkgs = import nixpkgs { inherit overlays system; };
+        xpkgs = import ./nixSupport/default.nix {
+          inherit pkgs;
+        };
+      in
+      rec {
+        packages = pkgs // xpkgs;
+        defaultPackage = xpkgs.librtti_debug;
+        devShells.default = pkgs.mkShell {
+          nativeBuildInputs = xpkgs.librtti.nativeBuildInputs;
+        };
+
+        devShell = self.devShells.${system}.default;
+      }
+    );
+}