src/core: move mach-core@9a4d09707d9f1cb6ea5602bdf58caeefc46146be package to here

Helps hexops/mach#1165

Signed-off-by: Stephen Gutekanst <stephen@hexops.com>

src/core/platform/wasm/entrypoint.zig

@@ -0,0 +1,42 @@
+// Check that the user's app matches the required interface.
+comptime {
+    if (!@import("builtin").is_test) @import("mach").core.AppInterface(@import("app"));
+}
+
+// Forward "app" declarations into our namespace, such that @import("root").foo works as expected.
+pub usingnamespace @import("app");
+const App = @import("app").App;
+
+const std = @import("std");
+const core = @import("mach").core;
+const gpu = core.gpu;
+
+pub const GPUInterface = gpu.StubInterface;
+
+var app: App = undefined;
+export fn wasmInit() void {
+    App.init(&app) catch |err| @panic(@errorName(err));
+}
+
+export fn wasmUpdate() bool {
+    if (core.update(&app) catch |err| @panic(@errorName(err))) {
+        return true;
+    }
+    return false;
+}
+
+export fn wasmDeinit() void {
+    app.deinit();
+}
+
+// Define std_options.logFn if the user did not in their "app" main.zig
+pub usingnamespace if (@hasDecl(App, "std_options")) struct {} else struct {
+    pub const std_options = struct {
+        pub const logFn = core.defaultLog;
+    };
+};
+
+// Define panic() if the user did not in their "app" main.zig
+pub usingnamespace if (@hasDecl(App, "panic")) struct {} else struct {
+    pub const panic = core.defaultPanic;
+};