cmake: make RelWithDebInfo the default configuration

CMakeLists.txt

@@ -1,5 +1,9 @@
 cmake_minimum_required(VERSION 3.16...3.28)
 
+if(NOT DEFINED CMAKE_BUILD_TYPE)
+    set(cmake_build_type_undefined 1)
+endif()
+
 list(APPEND CMAKE_MODULE_PATH "${CMAKE_CURRENT_LIST_DIR}/cmake")
 
 # See docs/release_checklist.md
@@ -28,6 +32,24 @@ else()
     set(SDLIMAGE_ROOTPROJECT OFF)
 endif()
 
+
+# By default, configure in RelWithDebInfo configuration
+if(NOT SDL3_SUBPROJECT)
+    get_property(is_multi_config GLOBAL PROPERTY GENERATOR_IS_MULTI_CONFIG)
+    if(is_multi_config)
+        # The first item in CMAKE_CONFIGURATION_TYPES is the default configuration
+        if(DEFINED CMAKE_CONFIGURATION_TYPES AND "RelWithDebInfo" IN_LIST CMAKE_CONFIGURATION_TYPES)
+            list(REMOVE_ITEM CMAKE_CONFIGURATION_TYPES "RelWithDebInfo")
+            list(INSERT CMAKE_CONFIGURATION_TYPES 0 "RelWithDebInfo")
+            set(CMAKE_CONFIGURATION_TYPES "${CMAKE_CONFIGURATION_TYPES}" CACHE STRING "CMake configuration types" FORCE)
+        endif()
+    else()
+        if(cmake_build_type_undefined)
+            set(CMAKE_BUILD_TYPE "RelWithDebInfo" CACHE STRING "CMake build type" FORCE)
+        endif()
+    endif()
+endif()
+
 set(SDLIMAGE_SAMPLES_DEFAULT ${SDLIMAGE_ROOTPROJECT})
 if(ANDROID)
     set(SDLIMAGE_SAMPLES_DEFAULT OFF)