lang/v8: fix build with libc++ 19
As noted in the libc++ 19 release notes [1], std::char_traits<> is now
only provided for char, char8_t, char16_t, char32_t and wchar_t, and any
instantiation for other types will fail.
This causes lang/v8 to fail to compile with clang 19 and libc++ 19,
resulting in errors similar to:
/usr/include/c++/v1/string:820:42: error: implicit instantiation of undefined template 'std::char_traits<unsigned short>'
820 | static_assert(is_same<_CharT, typename traits_type::char_type>::value,
| ^
../../src/inspector/v8-string-conversions.cc:387:26: note: in instantiation of template class 'std::basic_string<unsigned short>' requested here
387 | std::basic_string<UChar> UTF8ToUTF16(const char* stringStart, size_t length) {
| ^
/usr/include/c++/v1/__fwd/string.h:23:29: note: template is declared here
23 | struct _LIBCPP_TEMPLATE_VIS char_traits;
| ^Upstream v8 has fixed this in commit 182d9c05e78 [2], so add it as a
backported patch, until the next version of v8 is released.
[1] https://libcxx.llvm.org/ReleaseNotes/19.html#deprecations-and-removals
[2] https://chromium.googlesource.com/v8/v8.git/+/182d9c05e78
PR: 282514
Approved by: sunpoet (maintainer)
MFH: 2024Q4
(cherry picked from commit 1617a29594f0a2f73ca741638e97e591a6618365)