start making the src more wasm target aware

src/font/main.zig

@@ -56,8 +56,10 @@ pub const Backend = enum {
     /// Returns the default backend for a build environment. This is
     /// meant to be called at comptime.
     pub fn default() Backend {
-        // Wasm only supports browser at the moment.
-        if (builtin.target.isWasm()) return .web_canvas;
+        const wasm = @import("../os/wasm.zig");
+        if (wasm.target) |target| return switch (target) {
+            .browser => .web_canvas,
+        };
 
         return if (build_options.coretext)
             .coretext_freetype

src/os/wasm/log.zig

@@ -2,6 +2,13 @@ const std = @import("std");
 const builtin = @import("builtin");
 const wasm = @import("../wasm.zig");
 
+// Use the correct implementation
+pub usingnamespace if (wasm.target) |target| switch (target) {
+    .browser => Browser,
+} else struct {};
+
+/// Browser implementation calls an extern "log" function.
+pub const Browser = struct {
     // The function std.log will call.
     pub fn log(
         comptime level: std.log.Level,
@@ -38,3 +45,4 @@ pub fn log(
     const JS = struct {
         extern "env" fn log(ptr: [*]const u8, len: usize) void;
     };
+};