cmake: gate all preseeding behind SDL_PRESEED option

CMakeLists.txt

@@ -57,10 +57,6 @@ include("${SDL3_SOURCE_DIR}/cmake/PreseedEmscriptenCache.cmake")
 SDL_DetectCompiler()
 SDL_DetectTargetCPUArchitectures(SDL_CPUS)
 
-if (SDL_PRESEED_FUNCTION_DEFINED)
-  SDL_Preseed_CMakeCache()
-endif()
-
 # Increment this if there is an incompatible change - but if that happens,
 # we should rename the library from SDL3 to SDL4, at which point this would
 # reset to 0 anyway.
@@ -257,11 +253,17 @@ else()
   set(SDL_RPATH_DEFAULT OFF)
 endif()
 
+set(SDL_PRESEED_AVAILABLE OFF)
+if(COMMAND SDL_Preseed_CMakeCache)
+  set(SDL_PRESEED_AVAILABLE ON)
+endif()
+
 # Allow some projects to be built conditionally.
 set_option(SDL_DISABLE_INSTALL    "Disable installation of SDL3" ${SDL3_SUBPROJECT})
 cmake_dependent_option(SDL_DISABLE_INSTALL_CPACK "Create binary SDL3 archive using CPack" ${SDL3_SUBPROJECT} "NOT SDL_DISABLE_INSTALL" ON)
 cmake_dependent_option(SDL_DISABLE_INSTALL_DOCS "Install docs for SDL3" ON "NOT SDL_DISABLE_INSTALL;NOT SDL_FRAMEWORK" ON)
 set_option(SDL_DISABLE_UNINSTALL  "Disable uninstallation of SDL3" OFF)
+cmake_dependent_option(SDL_PRESEED "Preseed CMake cache to speed up configuration" ON "${SDL_PRESEED_AVAILABLE}" OFF)
 
 cmake_dependent_option(SDL_DISABLE_ANDROID_JAR  "Disable creation of SDL3.jar" ${SDL3_SUBPROJECT} "ANDROID" ON)
 
@@ -370,6 +372,10 @@ if(NOT (SDL_SHARED OR SDL_STATIC))
   message(FATAL_ERROR "SDL_SHARED and SDL_STATIC cannot both be disabled")
 endif()
 
+if(SDL_PRESEED)
+  SDL_Preseed_CMakeCache()
+endif()
+
 if(SDL_SHARED)
   add_library(SDL3-shared SHARED)
   add_library(SDL3::SDL3-shared ALIAS SDL3-shared)

cmake/PreseedEmscriptenCache.cmake

@@ -1,7 +1,4 @@
-cmake_dependent_option(SDL_EMSCRIPTEN_PRESEED "Preseed CMake cache for Emscripten to speed up configuration" ON "EMSCRIPTEN" OFF)
-
-if(SDL_EMSCRIPTEN_PRESEED)
-  set(SDL_PRESEED_FUNCTION_DEFINED TRUE)
+if(EMSCRIPTEN)
   function(SDL_Preseed_CMakeCache)
     set(COMPILER_SUPPORTS_FDIAGNOSTICS_COLOR_ALWAYS      "1"   CACHE INTERNAL "Test COMPILER_SUPPORTS_FDIAGNOSTICS_COLOR_ALWAYS")
     set(HAVE_ALLOCA_H                                    "1"   CACHE INTERNAL "Have include alloca.h")
@@ -177,4 +174,3 @@ if(SDL_EMSCRIPTEN_PRESEED)
     set(HAVE_DLOPEN_IN_LIBC                              "1"   CACHE INTERNAL "Have symbol dlopen")
   endfunction()
 endif()
-

cmake/PreseedMSVCCache.cmake

@@ -1,7 +1,4 @@
-cmake_dependent_option(SDL_MSVC_PRESEED "Preseed CMake cache for MSVC to speed up configuration" ON "MSVC;NOT WINDOWS_STORE" OFF)
-
-if(SDL_MSVC_PRESEED)
-  set(SDL_PRESEED_FUNCTION_DEFINED TRUE)
+if(MSVC)
   function(SDL_Preseed_CMakeCache)
     set(COMPILER_SUPPORTS_FDIAGNOSTICS_COLOR_ALWAYS      ""    CACHE INTERNAL "Test COMPILER_SUPPORTS_FDIAGNOSTICS_COLOR_ALWAYS")
     set(HAVE_ALLOCA_H                                    ""    CACHE INTERNAL "Have include alloca.h")