port rust tunnel example to zig

examples/zig/build.zig

@@ -0,0 +1,37 @@
+const std = @import("std");
+
+pub fn build(b: *std.build.Builder) void {
+    const mode = std.builtin.Mode.ReleaseSmall;
+
+    const lib = b.addSharedLibrary("cart", "main.zig", .unversioned);
+    lib.setBuildMode(mode);
+    lib.setTarget(.{ .cpu_arch = .wasm32, .os_tag = .freestanding });
+    lib.import_memory = true;
+    lib.initial_memory = 262144;
+    lib.max_memory = 262144;
+    lib.global_base = 81920;
+    lib.stack_size = 8192;
+    lib.install();
+
+    if (lib.install_step) |install_step| {
+        const run_filter_exports = b.addSystemCommand(&[_][]const u8{
+            "uw8", "filter-exports", "zig-out/lib/cart.wasm", "zig-out/lib/cart-filtered.wasm"
+        });
+        run_filter_exports.step.dependOn(&install_step.step);
+
+        const run_wasm_opt = b.addSystemCommand(&[_][]const u8{
+            "wasm-opt", "-Oz", "-o", "zig-out/cart.wasm", "zig-out/lib/cart-filtered.wasm"
+        });
+        run_wasm_opt.step.dependOn(&run_filter_exports.step);
+
+        const run_uw8_pack = b.addSystemCommand(&[_][]const u8{
+            "uw8", "pack", "-l", "9", "zig-out/cart.wasm", "zig-out/cart.uw8"
+        });
+        run_uw8_pack.step.dependOn(&run_wasm_opt.step);
+
+        const make_opt = b.step("make_opt", "make size optimized cart");
+        make_opt.dependOn(&run_uw8_pack.step);
+
+        b.default_step = make_opt;
+    }
+}