Update SDL2 to 2.28.5

libs/SDL2/CMakeLists.txt

@@ -87,7 +87,7 @@ endif()
 # See docs/release_checklist.md
 set(SDL_MAJOR_VERSION 2)
 set(SDL_MINOR_VERSION 28)
-set(SDL_MICRO_VERSION 4)
+set(SDL_MICRO_VERSION 5)
 set(SDL_VERSION "${SDL_MAJOR_VERSION}.${SDL_MINOR_VERSION}.${SDL_MICRO_VERSION}")
 
 # Set defaults preventing destination file conflicts
@@ -3089,9 +3089,17 @@ else()
   set(sdl_static_libname "SDL2")
 endif()
 
-set(prefix ${CMAKE_INSTALL_PREFIX})
+# CMAKE_PREFIX_PATH and CMAKE_INSTALL_FULL_BINDIR can be a non-absolute path
+# when a master-project does e.g. `set(CMAKE_INSTALL_PREFIX "libs/SDL2" CACHE PATH "prefix" FORCE)`.
+if(NOT IS_ABSOLUTE "${CMAKE_INSTALL_PREFIX}")
+  set(CMAKE_INSTALL_PREFIX "${CMAKE_BINARY_DIR}/${CMAKE_INSTALL_PREFIX}")
+endif()
+if(NOT IS_ABSOLUTE "${CMAKE_INSTALL_FULL_BINDIR}")
+  set(CMAKE_INSTALL_FULL_BINDIR "${CMAKE_BINARY_DIR}/${CMAKE_INSTALL_FULL_BINDIR}")
+endif()
 file(RELATIVE_PATH bin_prefix_relpath "${CMAKE_INSTALL_FULL_BINDIR}" "${CMAKE_INSTALL_PREFIX}")
 
+set(prefix ${CMAKE_INSTALL_PREFIX})
 set(exec_prefix "\${prefix}")
 set(libdir "\${exec_prefix}/${CMAKE_INSTALL_LIBDIR}")
 set(bindir "\${exec_prefix}/${CMAKE_INSTALL_BINDIR}")
@@ -3335,6 +3343,12 @@ if(ANDROID)
 endif()
 
 if(APPLE)
+  cmake_push_check_state(RESET)
+  check_c_compiler_flag(-fobjc-arc COMPILER_SUPPORTS_FOBJC_ARC)
+  cmake_pop_check_state()
+  if(NOT COMPILER_SUPPORTS_FOBJC_ARC)
+    message(FATAL_ERROR "Compiler does not support -fobjc-arc: this is required on Apple platforms")
+  endif()
   target_compile_options(sdl-build-options INTERFACE "-fobjc-arc")
 endif()