fix(cmake): don't pass -fno-fat-lto-objects on Apple GCC (#6114)

GCC on macOS has no linker plugin, so `-fno-fat-lto-objects` makes every
LTO probe fail and LTO is silently disabled. Plain `-flto=auto` works.

Fixes #6060

Assisted-by: ClaudeCode:claude-opus-5
Claude-Session: https://claude.ai/code/session_013JABmnjt9oAh29p1pytAB3
1 file changed