Fix build for Zig 0.18.0-dev.252+86dc5ce25

Zig 0.18.0-dev changed `standardOptimizeOption` to return an optional.
`optimize` will now be optional for older versions of Zig as well.

See: https://codeberg.org/ziglang/zig/pulls/36108

Author: jayschwa

build.zig

@@ -33,7 +33,9 @@ pub fn build(b: *std.Build) !void {
     // Get the upstream source and build options
     const upstream = b.dependency("sdl", .{});
     const target = b.standardTargetOptions(.{});
-    const optimize = b.standardOptimizeOption(.{});
+    // Coercing to an optional makes the value consistent across multiple versions of Zig.
+    // TODO: Remove explicit type annotation when Zig 0.18.0 is the minimum supported version.
+    const optimize: ?std.builtin.OptimizeMode = b.standardOptimizeOption(.{});
 
     const default_target_config = b.option(
         bool,
@@ -119,7 +121,7 @@ pub fn build(b: *std.Build) !void {
             // safe added.
             // https://wiki.libsdl.org/SDL3/SDL_ASSERT_LEVEL
             .SDL_DEFAULT_ASSERT_LEVEL_CONFIGURED = true,
-            .SDL_DEFAULT_ASSERT_LEVEL = @as(u2, switch (optimize) {
+            .SDL_DEFAULT_ASSERT_LEVEL = @as(u2, switch (optimize orelse std.builtin.OptimizeMode.Debug) {
                 .Debug, .ReleaseSafe => 2,
                 .ReleaseSmall, .ReleaseFast => 1,
             }),
@@ -146,7 +148,7 @@ pub fn build(b: *std.Build) !void {
     const translate_c = b.addTranslateC(.{
         .root_source_file = b.path("src/sdl.h"),
         .target = target,
-        .optimize = optimize,
+        .optimize = optimize orelse std.builtin.OptimizeMode.Debug,
     });
     translate_c.defineCMacro("USING_GENERATED_CONFIG_H", "1");
     translate_c.addIncludePath(upstream.path("include"));