This updates simdutf to my fork which has a SIMDUTF_NO_LIBCXX option
that removes all libc++ and libc++ ABI dependencies.
From there, the hand-written simd code we have has been updated to also
no longer use any libc++ features. Part of this required removing utfcpp
since it depended on libc++ (`<iterator>`).
libghostty-vt now only depends on libc.
The vendored Highway package was being built with libc++ even though
Ghostty only uses its runtime target selection and dispatch support.
That pulled in extra C++ runtime baggage from upstream support files
such as abort, timer, print, and benchmark helpers.
Build Highway in HWY_NO_LIBCXX mode, only compile the target dispatch
sources we actually need, and compile Ghostty's SIMD translation units
with the same define so the header ABI stays consistent. Replace the
upstream abort implementation with a small local bridge that provides
Highway's Warn/Abort hooks and the target-query shim without depending
on libc++.
This keeps the Highway archive down to the dispatch pieces Ghostty
uses while preserving the existing dynamic dispatch behavior. The
bridge is documented so it is clear why Ghostty carries this small
local replacement.
Zig's bundled libc++/libc++abi conflicts with the MSVC C++ runtime
headers (vcruntime_typeinfo.h, vcruntime_exception.h, etc.) when
targeting native-native-msvc. This caused compilation failures in
the SIMD C++ code due to -nostdinc++ suppressing MSVC headers and
libc++ types clashing with MSVC runtime types.
Skip linkLibCpp() for MSVC targets across all packages (highway,
simdutf, utfcpp) and the main build (SharedDeps, GhosttyZig) since
MSVC provides its own C++ standard library natively. Also add
missing <iterator> and <cstddef> includes that were previously
pulled in transitively through libc++ headers but are not
guaranteed by MSVC's headers.
