inital, almost working cross-compilation setup with Visual Studio and cmake

cmake/SDLSetup.cmake

@@ -0,0 +1,36 @@
+# Resolves pre-built SDL3 libraries based on PLATFORM and SDL_LINK_TYPE.
+# SDL must be pre-built once per platform via scripts/build_sdl_windows.ps1
+# or scripts/build_sdl_linux.sh before configuring this project.
+
+set(SDL_PREBUILT_DIR "${CMAKE_SOURCE_DIR}/prebuilt/${PLATFORM}")
+
+if(SDL_LINK_TYPE STREQUAL "static")
+    set(SDL_SEARCH_DIR "${SDL_PREBUILT_DIR}/SDL3-static")
+else()
+    set(SDL_SEARCH_DIR "${SDL_PREBUILT_DIR}/SDL3-dynamic")
+endif()
+
+message(STATUS "Looking for SDL3 in: ${SDL_SEARCH_DIR}")
+
+find_package(SDL3 REQUIRED CONFIG
+    PATHS "${SDL_SEARCH_DIR}"
+    NO_DEFAULT_PATH
+)
+
+if(SDL_LINK_TYPE STREQUAL "static")
+    set(SDL_TARGET SDL3::SDL3-static)
+else()
+    set(SDL_TARGET SDL3::SDL3)
+endif()
+
+message(STATUS "SDL_TARGET resolved to: ${SDL_TARGET}")
+
+# On Windows with dynamic linking, copy the DLL next to the executable
+if(SDL_LINK_TYPE STREQUAL "dynamic" AND WIN32)
+    add_custom_target(copy_sdl_dll ALL
+        COMMAND ${CMAKE_COMMAND} -E copy_if_different
+            $<TARGET_FILE:SDL3::SDL3>
+            "${CMAKE_BINARY_DIR}/game"
+        COMMENT "Copying SDL3.dll to output directory"
+    )
+endif()