cmake: don't enable LTO by default (#1548)

IPO/LTO creates faster code, but increases link time significantly.
People who just want to test Wicked should not have to read all
CMake options to see they can disable it for faster build time.

CMakeLists.txt

@@ -18,7 +18,6 @@ endif()
 project(WickedEngine)
 
 include(CheckIPOSupported)
-check_ipo_supported(RESULT ipo_supported)
 
 set(WICKED_ROOT_DIR ${CMAKE_CURRENT_SOURCE_DIR})
 
@@ -28,7 +27,7 @@ option(USE_LIBCXX "Link WickedEngine to llvm libc++ library - only available wit
 option(WICKED_EDITOR "Build WickedEngine editor" ON)
 option(WICKED_TESTS "Build WickedEngine tests" ON)
 option(WICKED_IMGUI_EXAMPLE "Build WickedEngine imgui example" ON)
-option(WICKED_ENABLE_IPO "Enable IPO/LTO in non-debug builds" ${ipo_supported})
+option(WICKED_ENABLE_IPO "Enable IPO/LTO in non-debug builds" NO)
 option(WICKED_EMBED_SHADERS "Embed shaders into the library" NO)
 if(UNIX)
     option(WICKED_ENABLE_ASAN "Enable AddressSanitizer in debug builds" OFF)