Add standalone exe build tooling under scripts/exe

build_exe.py compiles every unit in data/compile.json with the pinned toolchain and links Ragexe.exe.
Not part of the decompilation and not in data/compile.json: imports/*.def (original DLL import tables),
jsoncons/ (v0.170.2 headers + JsonCppLoader glue), nProtect/GameGuard.cpp (no-op GameGuard stand-in).

scripts/exe/nProtect/GameGuard.cpp

@@ -0,0 +1,31 @@
+// Stand-in for the nProtect GameGuard SDK, linked only into the standalone exe
+// built by scripts/exe/build_exe.py. Clank never compiles this file.
+//
+// The original statically links the SDK (0x00E8A000-0x00E96000). The client
+// reaches it through three entry points, called by CNProtectGameGuardMgr in
+// Source/Security/NProtectGameGuardMgr.cpp. This file provides those three with
+// the behaviour of a successful start-up, so the client follows the same path it
+// takes when GameGuard initialises normally. No anti-cheat checks are performed
+// and server GameGuard authentication requests are not answered.
+
+namespace {
+  // NPGAMEMON_SUCCESS: CNProtectGameGuardMgr treats any other status as a
+  // start-up failure.
+  constexpr int kGameGuardSuccess = 0x755;
+
+  int(__stdcall* g_callback)(int, const int*) = nullptr;
+}
+
+// fn_25538 (0x00E929B0): SDK initialisation.
+void sub_E929B0(const char*) {
+}
+
+// fn_25536 (0x00E92820): status of the last initialisation.
+int sub_E92820() {
+  return kGameGuardSuccess;
+}
+
+// fn_25543 (0x00E92E90): registers the client's GameGuard message handler.
+void sub_E92E90(int(__stdcall* callback)(int, const int*)) {
+  g_callback = callback;
+}