build.zig: use the options for setting the use_llvm flags

build.zig

@@ -3,17 +3,16 @@ const std = @import("std");
 pub fn build(b: *std.Build) void {
     const target = b.standardTargetOptions(.{});
     const optimize = b.standardOptimizeOption(.{});
-
     const use_llvm = b.option(bool, "use-llvm", "use the LLVM backend");
 
     const exe = b.addExecutable(.{
         .name = "tetris",
         .root_source_file = b.path("src/main.zig"),
         .optimize = optimize,
         .target = target,
+        .use_llvm = use_llvm,
+        .use_lld = use_llvm,
     });
-    exe.use_llvm = use_llvm;
-    exe.use_lld = use_llvm;
 
     exe.linkLibC();
     exe.linkSystemLibrary("glfw");