Roll libc++ from 25731e23e3aa to 91c45fc28459 (2 revisions)

The string_view nodiscard change requires updating
absl_hardening_test.cc with a few "unused result" warning
suppressions. Since that's a downstream file, we can just change
the file.

https://chromium.googlesource.com/external/github.com/llvm/llvm-project/libcxx.git/+log/25731e23e3aa..91c45fc28459

2025-11-24 [email protected] [libcxx] [test] Fix the gets-removed.verify.cpp test with Clang 21 (#169235)
2025-11-24 [email protected] [libc++][string_view] Applied `[[nodiscard]]` (#169010)

If this roll has caused a breakage, revert this CL and stop the roller
using the controls here:
https://autoroll.skia.org/r/libcxx-chromium
Please CC [email protected],[email protected] on the revert to ensure that a human
is aware of the problem.

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To report a problem with the AutoRoller itself, please file a bug:
https://issues.skia.org/issues/new?component=1389291&template=1850622

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Change-Id: Ia9bb68516c2f46f76bfd639941c81b3ab13b4f30
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/7201143
Reviewed-by: Hans Wennborg <[email protected]>
Commit-Queue: Nico Weber <[email protected]>
Reviewed-by: Mirko Bonadei <[email protected]>
Cr-Commit-Position: refs/heads/main@{#1551059}
NOKEYCHECK=True
GitOrigin-RevId: 3a229aacd71ba47d349c5bc99f4abab9d4a9a3c9

Author: nico

deps_revisions.gni

@@ -5,5 +5,5 @@
 declare_args() {
   # Used to cause full rebuilds on libc++ rolls. This should be kept in sync
   # with the libcxx_revision var in //DEPS.
-  libcxx_revision = "25731e23e3aae8f833705d3b2e6540d7d5eab3e0"
+  libcxx_revision = "91c45fc28459e814889633be985b698c5e8050b4"
 }

third_party/libc++/libcxx_headers.gni

@@ -11,7 +11,7 @@
 import("//buildtools/deps_revisions.gni")
 
 assert(
-    libcxx_revision == "25731e23e3aae8f833705d3b2e6540d7d5eab3e0",
+    libcxx_revision == "91c45fc28459e814889633be985b698c5e8050b4",
     "libcxx_headers.gni and third_party/libc++ are out of sync.$0x0A$0x0AIf you were messing around with the libc++ repository, run:$0x0A`buildtools/third_party/libc++/generate_libcxx_headers.py`$0x0A$0x0AIf the script doesn't resolve the error, file a bug to msta@ with reproduction details.$0x0A")
 
 libcxx_headers = [