Evaluate patches

[jserv]

I have been working on cortexm-linux, a QEMU-based testbed. There are some patches worth reviewing and adopting.

• LTO
• ICF
• partial Linux Tiny patches

[jserv]

LTO patch from cortexm-linux should be slightly better for code size optimization. In addition, 0005-debloat-proc.patch can help reduce.

[jserv]

introduces an UNWINDER_NONE choice option to drop the ARM EABI unwind tables (.ARM.exidx and .ARM.extab, ~75KB). On THUMB2_KERNEL neither UNWINDER_FRAME_POINTER (depends on !THUMB2_KERNEL) nor UNWINDER_NONE existed, and THUMB2_KERNEL itself unconditionally selected ARM_UNWIND.

[jserv]

0012-tiny-sched-no-debug-output.patch and 0013-tiny-sched-no-deadline-class.patch reduce unintended scheduler code waste.

[jserv]

Major rework on CPU scheduler:

• Replace CFS/EEVDF with compact O(1) tiny scheduler
• Strip residual sched/time surface after fair-tiny