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 martin@martin.st [libcxx] [test] Fix the gets-removed.verify.cpp test with Clang 21 (#169235)
2025-11-24 hghristov.rmm@gmail.com [libc++][string_view] Applied `[[nodiscard]]` (#169010)

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https://autoroll.skia.org/r/libcxx-chromium
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Change-Id: Ia9bb68516c2f46f76bfd639941c81b3ab13b4f30
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/7201143
Reviewed-by: Hans Wennborg <hans@chromium.org>
Commit-Queue: Nico Weber <thakis@chromium.org>
Reviewed-by: Mirko Bonadei <mbonadei@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1551059}
NOKEYCHECK=True
GitOrigin-RevId: 3a229aacd71ba47d349c5bc99f4abab9d4a9a3c9
diff --git a/absl_hardening_test.cc b/absl_hardening_test.cc
index 561f334..6c4fcb1 100644
--- a/absl_hardening_test.cc
+++ b/absl_hardening_test.cc
@@ -27,13 +27,13 @@
 
 TEST(AbslHardeningTest, StringView) {
   absl::string_view view("foo");
-  EXPECT_DEATH_IF_SUPPORTED(view[4], "");
+  EXPECT_DEATH_IF_SUPPORTED(std::ignore = view[4], "");
   EXPECT_DEATH_IF_SUPPORTED(view.remove_prefix(10), "");
   EXPECT_DEATH_IF_SUPPORTED(view.remove_suffix(10), "");
 
   absl::string_view empty("");
-  EXPECT_DEATH_IF_SUPPORTED(empty.front(), "");
-  EXPECT_DEATH_IF_SUPPORTED(empty.back(), "");
+  EXPECT_DEATH_IF_SUPPORTED(std::ignore = empty.front(), "");
+  EXPECT_DEATH_IF_SUPPORTED(std::ignore = empty.back(), "");
 }
 
 TEST(AbslHardeningTest, FixedArray) {