try to fix the libc++ build

Author: cor3ntin

libcxx/test/std/algorithms/alg.nonmodifying/alg.equal/equal.pass.cpp

@@ -19,7 +19,9 @@
 //   equal(Iter1 first1, Iter1 last1, Iter2 first2, Iter2 last2);
 
 // We test the cartesian product, so we sometimes compare differently signed types
-// ADDITIONAL_COMPILE_FLAGS(gcc-style-warnings): -Wno-sign-compare -Wno-implicit-unicode-conversion
+// ADDITIONAL_COMPILE_FLAGS(gcc-style-warnings): -Wno-sign-compare
+// ADDITIONAL_COMPILE_FLAGS(clang-21): -Wno-implicit-unicode-conversion
+
 // MSVC warning C4242: 'argument': conversion from 'int' to 'const _Ty', possible loss of data
 // MSVC warning C4244: 'argument': conversion from 'wchar_t' to 'const _Ty', possible loss of data
 // MSVC warning C4389: '==': signed/unsigned mismatch

libcxx/test/std/algorithms/alg.nonmodifying/alg.find/find.pass.cpp

@@ -7,7 +7,8 @@
 //===----------------------------------------------------------------------===//
 
 // ADDITIONAL_COMPILE_FLAGS(gcc): -Wno-bool-compare
-// ADDITIONAL_COMPILE_FLAGS(gcc-style-warnings): -Wno-sign-compare -Wno-implicit-unicode-conversion
+// ADDITIONAL_COMPILE_FLAGS(gcc-style-warnings): -Wno-sign-compare
+// ADDITIONAL_COMPILE_FLAGS(clang-21): -Wno-implicit-unicode-conversion
 // MSVC warning C4245: conversion from 'int' to 'wchar_t', signed/unsigned mismatch
 // MSVC warning C4305: truncation from 'int' to 'bool'
 // MSVC warning C4310: cast truncates constant value