Harden x86 FP setup and isolate FP build flags
* Enable FXSAVE/FXRSTOR-backed FPU context handling with alignment-safe helpers and CR4 OSXMMEXCPT setup; require SSE/FXSR on x86_32
* Move no-SSE/no-MMX compilation flags out of global CC_BASE into x86 kernel/boot/UEFI build rules
* Guard kernel allocator and scheduler startup critical sections with IRQ save/restore to avoid early races
* Add a QEMU snapshot toggle (default on) and keep user FP flags local to user build config
10 files changed,
146 insertions,
11 deletions