My project normally builds without any problems with Xcode 16.4, but after I upgraded to Xcode 26.4, I encountered the error below.
I have the same issue, I downloaded XCode 26.3 from apple website and it currently solved this for a while.
how you fix it @enj0y ?
Download previous version of XCode from: https://developer.apple.com/services-account/download?path=/Developer_Tools/Xcode_26.3/Xcode_26.3_Apple_silicon.xip
There are also fix for XCode 26.4, but you will need to patch “/CocosCreator.app/Contents/Resources/resources/3d/engine/native/external/ios/libs/libwebp.a” 
What do you mean this ? i cant downgrade xcode to 26.3, but have bug with libwebp.a too 
I did this fix for libwebp:
mkdir /tmp/webp_fix && cd /tmp/webp_fix
# Backup original
cp "/Applications/Cocos/Creator/3.8.8/CocosCreator.app/Contents/Resources/resources/3d/engine/native/external/ios/libs/libwebp.a" \
"/Applications/Cocos/Creator/3.8.8/CocosCreator.app/Contents/Resources/resources/3d/engine/native/external/ios/libs/libwebp.a.bak"
# Extract arm64
lipo "/Applications/Cocos/Creator/3.8.8/CocosCreator.app/Contents/Resources/resources/3d/engine/native/external/ios/libs/libwebp.a" \
-thin arm64 \
-output libwebp_arm64.a
# Extract all objects from the archive
ar -x libwebp_arm64.a
# Recreate with macOS libtool (handles alignment correctly)
libtool -static -o libwebp_fixed.a *.o
# Replace
cp libwebp_fixed.a "/Applications/Cocos/Creator/3.8.8/CocosCreator.app/Contents/Resources/resources/3d/engine/native/external/ios/libs/libwebp.a"
And if you want to patch for XCode 26.4:
/Applications/Cocos/Creator/3.8.8/CocosCreator.app/Contents/Resources/resources/3d/engine/native/external/sources/enoki/half.h
#if !(defined(_LIBCPP_VERSION) && _LIBCPP_VERSION >= 180000) && (__cplusplus < 202302L)
NAMESPACE_BEGIN(std)
template<> struct is_floating_point<enoki::half> : true_type { };
template<> struct is_arithmetic<enoki::half> : true_type { };
template<> struct is_signed<enoki::half> : true_type { };
NAMESPACE_END(std)
#endif