fix(sdk): add apple2 lazyDeps and missing save_basic to commodore/mega65

ref.: llvm-mos/llvm-mos-sdk#430

Author: kassane

build.zig

@@ -43,7 +43,6 @@ pub fn build(b: *std.Build) void {
     // llvm-mos-sdk git source — always required for headers, linker scripts, and platform libs.
     const sdk_dep = b.dependency("llvm-mos-sdk", .{});
     const sdk_src_raw = sdk_dep.path(".").getPath(b);
-    const apple2_dep = b.dependency("apple2", .{});
     // Normalize separators for embedding in linker scripts and assembly (.incbin).
     const sdk_src = blk: {
         const buf = b.allocator.dupe(u8, sdk_src_raw) catch @panic("OOM");
@@ -717,7 +716,7 @@ pub fn build(b: *std.Build) void {
     }
 
     // ---- Apple2 hello ----
-    {
+    if (b.lazyDependency("apple2", .{})) |apple2_dep| {
         const step = b.step("apple2-hello", "Build Apple IIe hello example");
         const exe = addApple2Exe(b, sdk_src, apple2_dep, optimize);
         const install = b.addInstallArtifact(exe, .{ .dest_sub_path = "hello.sys" });
@@ -1682,6 +1681,7 @@ fn addMega65Exe(
     exe.root_module.linkLibrary(libs.c);
     if (libs.crt0_obj) |obj| exe.root_module.addObject(obj);
     if (libs.mem) |mem_obj| exe.root_module.addObject(mem_obj);
+    if (libs.save_basic) |sb_obj| exe.root_module.addObject(sb_obj);
     exe.forceUndefinedSymbol("__zig_call_main_section");
     exe.forceUndefinedSymbol("main");
     exe.setLibCFile(libc_txt);

build.zig.zon

@@ -14,6 +14,7 @@
         .apple2 = .{
             .url = "git+https://github.com/TheHans255/apple-ii-port-work#31fde9997cfb4a5e98a9d0fc0efaf869fbedeb1f",
             .hash = "N-V-__8AAIzPAQDlio9aQBDM199SjX-qme9i0IIUuqp2IX0v",
+            .lazy = true,
         },
     },
     .minimum_zig_version = "0.16.0",

sdk/build.zig

@@ -38,6 +38,9 @@ pub const Libs = struct {
     crt0_obj2: ?*std.Build.Step.Compile = null,
     // NES only: FamiTone2 music/sound engine + banked fixed-bank wrappers.
     famitone2: ?*std.Build.Step.Compile = null,
+    // MEGA65/Commodore: save-basic.S saves/restores ZP and overrides _Exit to return
+    // cleanly to BASIC. Must be a TRUE object (section-only .init.005/.fini.989).
+    save_basic: ?*std.Build.Step.Compile = null,
 };
 
 /// Build platform libraries for `pd` from the SDK source tree at `sdk_root`.
@@ -249,7 +252,25 @@ pub fn buildPlatform(b: *std.Build, sdk_root: []const u8, pd: Platform, opt: std
             .files = &.{"crt0.S"},
         });
         crt0_obj.lto = .none;
-        return .{ .crt = libcrt, .crt0 = libcrt0, .c = libc, .printf = libprintf, .mem = mem_obj, .crt0_obj = crt0_obj };
+        // save-basic.S: TRUE object for MEGA65/Commodore clean BASIC exit (PR #430).
+        // Contains .init.005 (save ZP) and .fini.989 (restore ZP) section-only contributions
+        // with no exported symbol → must be a TRUE object, not an archive member (Hard rule #5).
+        var save_basic_obj: ?*std.Build.Step.Compile = null;
+        if (std.mem.eql(u8, pd.name, "mega65")) {
+            const sb_obj = b.addObject(.{
+                .name = "save-basic",
+                .root_module = b.createModule(.{ .target = target, .optimize = opt }),
+            });
+            sb_obj.root_module.addIncludePath(.{ .cwd_relative = com_asm });
+            sb_obj.root_module.addIncludePath(.{ .cwd_relative = com_inc });
+            sb_obj.root_module.addCSourceFiles(.{
+                .root = .{ .cwd_relative = comm_dir },
+                .files = &.{"save-basic.S"},
+            });
+            sb_obj.lto = .none;
+            save_basic_obj = sb_obj;
+        }
+        return .{ .crt = libcrt, .crt0 = libcrt0, .c = libc, .printf = libprintf, .mem = mem_obj, .crt0_obj = crt0_obj, .save_basic = save_basic_obj };
     }
 
     return .{ .crt = libcrt, .crt0 = libcrt0, .c = libc };