cmake: explicitly disable UNITY_BUILD property for SDL3 libraries

CMakeLists.txt

@@ -448,6 +448,7 @@ if(SDL_SHARED)
   add_library(SDL3-shared SHARED)
   add_library(SDL3::SDL3-shared ALIAS SDL3-shared)
   SDL_AddCommonCompilerFlags(SDL3-shared)
+  set_property(TARGET SDL3-shared PROPERTY UNITY_BUILD OFF)
   if ("c_std_99" IN_LIST CMAKE_C_COMPILE_FEATURES)
     target_compile_features(SDL3-shared PRIVATE c_std_99)
   else()
@@ -459,6 +460,7 @@ if(SDL_STATIC)
   add_library(SDL3-static STATIC)
   add_library(SDL3::SDL3-static ALIAS SDL3-static)
   SDL_AddCommonCompilerFlags(SDL3-static)
+  set_property(TARGET SDL3-static PROPERTY UNITY_BUILD OFF)
   if ("c_std_99" IN_LIST CMAKE_C_COMPILE_FEATURES)
     target_compile_features(SDL3-static PRIVATE c_std_99)
   else()
@@ -1228,6 +1230,7 @@ target_include_directories(SDL_uclibc PRIVATE "${SDL3_SOURCE_DIR}/src")
 target_include_directories(SDL_uclibc PRIVATE "${SDL3_SOURCE_DIR}/include")
 SDL_AddCommonCompilerFlags(SDL_uclibc)
 sdl_sources(STATIC "$<TARGET_OBJECTS:SDL_uclibc>")
+set_property(TARGET SDL_uclibc PROPERTY UNITY_BUILD OFF)
 if(TARGET SDL3-shared)
   target_link_libraries(SDL3-shared PRIVATE SDL_uclibc)
 endif()