Roll llvm-libc from 38934b6b615c to 9afb8940697a (14 revisions)

https://chromium.googlesource.com/external/github.com/llvm/llvm-project/libc.git/+log/38934b6b615c..9afb8940697a

2026-10-16 lntue@google.com [libc][math] Fix code size issues with sinf and cosf. (#232843)
2026-10-16 lntue@google.com [libc][math] Optimize exp2 and refactor shared double-precision exp utilities. (#231041)
2026-10-16 lntue@google.com [libc][math] Fix code size issues for powf_float_eval. (#232601)
2026-10-16 lntue@google.com [libc][math] Remove unneccessary checks and speedup for pow_fast under LIBC_MATH_HAS_SMALL_TABLES. (#232623)
2026-10-16 pavel@labath.sk [libc] Add SCM_TIMESTAMP constants (#232688)
2026-10-16 jbailey@raspberryginger.com [libc][regex] Wire regex entrypoints to ExprPool matcher (#232291)
2026-10-16 lntue@google.com [libc][cmake] Fix and enhance LibcParseArguments and add unified libc_log helper (#232089)
2026-10-16 pavel@labath.sk [libc] Move linux signal mask helpers into OSUtil/sigmask.h (#232647)
2026-10-16 simon.tatham@arm.com [libc][printf] Fix %e/%g formatting in float320 algorithm (#232721)
2026-10-16 pavel@labath.sk [libc] Block signals before a detached thread unmaps its stack (#232649)
2026-10-16 c8ef@outlook.com [libc] Use a syscall wrapper for `sched_getparam` (#232689)
2026-10-16 pavel@labath.sk [libc] Define IFNAMSIZ in net/if.h (#232664)
2026-10-16 jbailey@raspberryginger.com [libc] Add <libintl.h> and textdomain stub (#232351)
2026-10-16 c8ef@outlook.com [libc] Use a syscall wrapper for `sched_getscheduler` (#232597)

If this roll has caused a breakage, revert this CL and set the roller
to dry run mode using the controls here:
https://autoroll.skia.org/r/llvm-libc-chromium
Please CC lexan@google.com,yueshe@google.com on the revert to ensure that a human
is aware of the problem.

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https://issues.skia.org/issues/new?component=1389291&template=1850622

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https://skia.googlesource.com/buildbot/+doc/main/autoroll/README.md

Tbr: yueshe@google.com
Change-Id: I7fd5891ab873508f092a8a4182bcd69db2c87d02
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/8601875
Bot-Commit: chromium-autoroll@skia-public.iam.gserviceaccount.com <chromium-autoroll@skia-public.iam.gserviceaccount.com>
Commit-Queue: chromium-autoroll@skia-public.iam.gserviceaccount.com <chromium-autoroll@skia-public.iam.gserviceaccount.com>
Cr-Commit-Position: refs/heads/main@{#1721316}
NOKEYCHECK=True
GitOrigin-RevId: acd5142da4e6a90b9f41150c98639ce65b1a2cff