Making GetWindowHandle() return as the IntPtr of glfwGetX11Display();

[ReDarkTechnology]

So I have some sort of need to get the X11Display of the current window that Raylib creates so I cloned the source code and changed this part on the rcore_desktop_glfw.c to return this instead

// Get native window handle
void *GetWindowHandle(void)
{
#if defined(_WIN32)
    // NOTE: Returned handle is: void *HWND (windows.h)
    return glfwGetWin32Window(platform.handle);
#endif
#if defined(__linux__)
    return (void *)(uintptr_t)glfwGetX11Display();
#endif
#if defined(__APPLE__)
    // NOTE: Returned handle is: (objc_object *)
    return (void *)glfwGetCocoaWindow(platform.handle);
#endif

    return NULL;
}

But when I compiled it, it complains about implicit typing:

$ make PLATFORM=PLATFORM_DESKTOP RAYLIB_LIBTYPE=SHARED # To make the dynamic shared version.
gcc -c rcore.c -Wall -D_GNU_SOURCE -DPLATFORM_DESKTOP_GLFW -DGRAPHICS_API_OPENGL_33 -Wno-missing-braces -Werror=pointer-arith -fno-strict-aliasing -std=c99 -fPIC -O1 -Werror=implicit-function-declaration -fPIC -DBUILD_LIBTYPE_SHARED -fvisibility=hidden -D_GLFW_X11  -I.  -Iexternal/glfw/include
In file included from rcore.c:554:
platforms/rcore_desktop_glfw.c: In function ‘GetWindowHandle’:
platforms/rcore_desktop_glfw.c:707:31: error: implicit declaration of function ‘glfwGetX11Display’ [-Werror=implicit-function-declaration]
  707 |     return (void *)(uintptr_t)glfwGetX11Display();
      |                               ^~~~~~~~~~~~~~~~~
rcore.c: In function ‘LoadAutomationEventList’:
rcore.c:2932:13: warning: ignoring return value of ‘fgets’ declared with attribute ‘warn_unused_result’ [-Wunused-result]
 2932 |             fgets(buffer, 256, raeFile);
      |             ^~~~~~~~~~~~~~~~~~~~~~~~~~~
rcore.c:2949:17: warning: ignoring return value of ‘fgets’ declared with attribute ‘warn_unused_result’ [-Wunused-result]
 2949 |                 fgets(buffer, 256, raeFile);
      |                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~
cc1: some warnings being treated as errors
make: *** [Makefile:741: rcore.o] Error 1

I'm using Linux Mint Cinnamon to build this
How do I make it build, I've never really worked with a C library before, thank you 🙏