stage2: wire up -Dskip-non-native

The purpose of this is to save time in the edit-compile-test cycle when
working on stage2 code.

build.zig

@@ -83,6 +83,7 @@ pub fn build(b: *Builder) !void {
     test_step.dependOn(&exe.step);
     b.default_step.dependOn(&exe.step);
 
+    exe.addBuildOption(bool, "skip_non_native", skip_non_native);
     exe.addBuildOption(bool, "have_llvm", enable_llvm);
     if (enable_llvm) {
         const config_h_text = if (config_h_path_option) |config_h_path|
@@ -166,6 +167,7 @@ pub fn build(b: *Builder) !void {
     const is_wasmtime_enabled = b.option(bool, "enable-wasmtime", "Use Wasmtime to enable and run WASI libstd tests") orelse false;
     const glibc_multi_dir = b.option([]const u8, "enable-foreign-glibc", "Provide directory with glibc installations to run cross compiled tests that link glibc");
 
+    test_stage2.addBuildOption(bool, "skip_non_native", skip_non_native);
     test_stage2.addBuildOption(bool, "is_stage1", false);
     test_stage2.addBuildOption(bool, "have_llvm", enable_llvm);
     test_stage2.addBuildOption(bool, "enable_qemu", is_qemu_enabled);

src/codegen.zig

@@ -16,6 +16,7 @@ const trace = @import("tracy.zig").trace;
 const DW = std.dwarf;
 const leb128 = std.leb;
 const log = std.log.scoped(.codegen);
+const build_options = @import("build_options");
 
 /// The codegen-related data that is stored in `ir.Inst.Block` instructions.
 pub const BlockData = struct {
@@ -427,6 +428,10 @@ fn Function(comptime arch: std.Target.Cpu.Arch) type {
             code: *std.ArrayList(u8),
             debug_output: DebugInfoOutput,
         ) GenerateSymbolError!Result {
+            if (build_options.skip_non_native and std.Target.current.cpu.arch != arch) {
+                @panic("Attempted to compile for architecture that was disabled by build configuration");
+            }
+
             const module_fn = typed_value.val.cast(Value.Payload.Function).?.func;
 
             const fn_type = module_fn.owner_decl.typed_value.most_recent.typed_value.ty;

src/config.zig.in

@@ -4,3 +4,4 @@ pub const log_scopes: []const []const u8 = &[_][]const u8{};
 pub const zir_dumps: []const []const u8 = &[_][]const u8{};
 pub const enable_tracy = false;
 pub const is_stage1 = true;
+pub const skip_non_native = false;