Strip residual sched/time surface after fair-tiny

[jserv]

6 out-of-tree patches stack on top of 0014 to land another 16,416 bytes of linux.axf (-14,528 of resident .text):

0015 SCHED_TOPOLOGY_MINIMAL (default n; set y)
Wraps kernel/sched/topology.c in #ifndef and substitutes a
minimal stub: def_root_domain + init_rootdomain +
init_defrootdomain + rq_attach_root + sched_get/put_rd +
sched_domains_mutex helpers + empty sched_init_domains and
partition_sched_domains. Drops sched_domain construction,
NUMA, perf-domain, asym-capacity, and topology debug.
topology.c 5,028 -> 70 B / 23 -> 6 syms.

0016 SCHED_NO_RICH_API (default n; set y)
Gates 11 SYSCALL_DEFINEs in kernel/sched/syscalls.c
(sched_set/getparam, set/getscheduler, set/getattr,
set/getaffinity, get_priority_{max,min}, rr_get_interval).
sys_ni.c gains COND_SYSCALL aliases so each slot returns
-ENOSYS. Internal helpers (sched_set_fifo*,
sched_setscheduler_nocheck, sched_setattr_nocheck,
sched_setaffinity, sched_getaffinity, __sched_setaffinity,
dl_task_check_affinity) stay live for RCU / kthread / compat
callers. sched_yield (158) and nice (34) unaffected.
syscalls.c 3,192 -> 2,068 B / 41 -> 21 syms.

0017 POSIX_CPU_TIMERS (default y; set n)
Wraps kernel/time/posix-cpu-timers.c in #ifdef and
substitutes k_clock dispatch tables for clock_process /
clock_thread / clock_posix_cpu that return -EINVAL via four
shared stub methods, plus no-op stubs for
posix_cputimers_group_init, run_posix_cpu_timers,
update_rlimit_cpu, thread_group_sample_cputime,
set_process_cpu_timer, posix_cpu_timers_exit{,_group}.
Effective syscall impact: clock_gettime / clock_getres /
clock_nanosleep on CLOCK_PROCESS_CPUTIME_ID and
CLOCK_THREAD_CPUTIME_ID return -EINVAL; setrlimit(RLIMIT_CPU)
and ITIMER_PROF / ITIMER_VIRTUAL become silent no-ops.
posix-cpu-timers.c 3,722 -> 66 B / 42 -> 11 syms.

0018 SCHED_PELT_RT_MINI (default n; set y)
Stubs CFS-side (__update_load_avg_blocked_se / _se / _cfs_rq)
and DL-side (update_dl_rq_load_avg) PELT entry points in
kernel/sched/pelt.c to return 0; update_other_load_avgs
collapses to a thin call into update_rt_rq_load_avg. Helpers
(decay_load, __accumulate_pelt_segments, accumulate_sum,
___update_load_sum, ___update_load_avg, runnable_avg_yN_inv)
stay live for rt.c. Combined with 0019, all of pelt.c
becomes LTO-strippable. pelt.c 1,758 -> 470 B / 8 -> 7 syms.

0019 SCHED_RT_TINY (default n; set y)
Wraps kernel/sched/rt.c in #ifndef and substitutes a fixed-
priority FIFO class reusing the existing rt_rq->active
priority-bitmap + per-priority list_head data structure.
Drops SCHED_RR slice rotation (RR collapses to FIFO), RT
bandwidth period/runtime timer, throttle, push/pull migration
(UP-only target makes the migration surface dead),
cpupri-driven find_lowest_rq, and sched_rt/rr_handler sysctl
writers. Cross-priority preemption stays via resched_curr;
RT > fair preemption stays via the class-chain walk.
get_rr_interval_rt returns 0 for SCHED_FIFO (mainline
contract). rt.c 3,400 -> 606 B / 34 -> 16 syms.

0020 TIME_NO_SET_WALLCLOCK (default n; set y)
Short-circuits do_settimeofday64, do_adjtimex, and
timekeeping_warp_clock in kernel/time/timekeeping.c.
Effective userspace impact: settimeofday(2),
clock_settime(2), adjtimex(2), and stime(2) all return
-EPERM; clock_gettime(2) read paths stay live. NTP
discipline / leap-second / TAI helpers lose all in-tree
callers and become candidates for LTO dead-stripping.

build.sh: extend the apply_patch_once loop, set the 6 new Kconfigs (five =y, POSIX_CPU_TIMERS =n), extend the post-olddefconfig verification list.

Cumulative on the production build: vmlinux .text 755,888 ->
746,484 (-9,404), resident .text (subsystem-rollup) 713,412 -> 698,884 (-14,528), linux.axf 1,188,352 -> 1,171,936 (-16,416 / 4 pages). Per-bucket: kernel/sched 30,980 -> 21,568 (-30.4%), kernel/time 39,442 -> 35,446 (-10.1%).

Each patch boot-tested independently in QEMU MPS2-AN386 (busybox sleep, date, ps; background CPU hog plus interactive shell coexistence verified for 0019).