Don't force symbol export if code mods disabled

Allows us to re-enable PCH on RmlUI. We'll likely need to rethink how this works anyways IMO.

src/dusk/launcher_win32.cpp

@@ -8,7 +8,7 @@
 #include <Windows.h>
 
 // see src/dusk/main.cpp
-extern "C" int WINAPI dusk_WinMain(HINSTANCE hInst, HINSTANCE hPrev, PWSTR cmd, int show);
+int dusk_WinMain(HINSTANCE hInst, HINSTANCE hPrev, PWSTR cmd, int show);
 
 int WINAPI wWinMain(HINSTANCE hInst, HINSTANCE hPrev, PWSTR cmd, int show) {
     return dusk_WinMain(hInst, hPrev, cmd, show);

src/dusk/main.cpp

@@ -225,7 +225,7 @@ int main(int argc, char* argv[]) {
 
 #if _WIN32
 // Entry point called by the launcher executable.
-extern "C" int WINAPI dusk_WinMain(HINSTANCE, HINSTANCE, PWSTR, int) {
+int __declspec(dllexport) dusk_WinMain(HINSTANCE, HINSTANCE, PWSTR, int) {
     return RunWindowsGuiEntryPoint();
 }
 #endif