[cmake] Start requiring SDL2 (#3632)

Closes #3466

Like said in the issue and the OpenSSL equivalent, disabling SDL2 on
desktop is just not something we want to do. It's not worth the added
burden of supporting the n+1'th matrix.

Signed-off-by: crueter <crueter@eden-emu.dev>
Reviewed-on: https://git.eden-emu.dev/eden-emu/eden/pulls/3632
Reviewed-by: CamilleLaVey <camillelavey99@gmail.com>
Reviewed-by: MaranBr <maranbr@eden-emu.dev>

src/yuzu/main_window.cpp

@@ -149,9 +149,7 @@ static FileSys::VirtualFile VfsDirectoryCreateFileWrapper(const FileSys::Virtual
 #include "video_core/renderer_base.h"
 #include "video_core/shader_notify.h"
 
-#ifdef HAVE_SDL2
 #include <SDL.h>
-#endif
 
 #include <boost/container/flat_set.hpp>
 
@@ -602,7 +600,7 @@ MainWindow::MainWindow(bool has_broken_vulkan)
         VkDeviceInfo::PopulateRecords(vk_device_records, this->window()->windowHandle());
     }
 
-#if defined(HAVE_SDL2) && !defined(_WIN32)
+#if !defined(_WIN32)
     SDL_InitSubSystem(SDL_INIT_VIDEO);
 
     // Set a screensaver inhibition reason string. Currently passed to DBus by SDL and visible to
@@ -1881,7 +1879,7 @@ void MainWindow::OnSigInterruptNotifierActivated() {
 void MainWindow::PreventOSSleep() {
 #ifdef _WIN32
     SetThreadExecutionState(ES_CONTINUOUS | ES_SYSTEM_REQUIRED | ES_DISPLAY_REQUIRED);
-#elif defined(HAVE_SDL2)
+#else
     SDL_DisableScreenSaver();
 #endif
 }
@@ -1889,7 +1887,7 @@ void MainWindow::PreventOSSleep() {
 void MainWindow::AllowOSSleep() {
 #ifdef _WIN32
     SetThreadExecutionState(ES_CONTINUOUS);
-#elif defined(HAVE_SDL2)
+#else
     SDL_EnableScreenSaver();
 #endif
 }