## Why
The Bazel V8 source build supported Windows GNU but lacked an MSVC-targeting toolchain to produce `*-pc-windows-msvc` archives.
## What changed
- Add opt-in archive targets for native Windows x64 and ARM64 hosts, selected by `//third_party/v8:rusty_v8_native_windows_archive_for_target`.
- Fetch pinned LLVM and scope its `clang-cl` toolchain to V8 artifacts, using the installed Microsoft SDK. Bundle Chromium libc++ and compiler-rt builtins into the resulting `.lib`.
- Adapt V8 dependencies, assembly, snapshot generation, and platform feature settings for MSVC, and derive test metadata from the selected engine features.
- Document the native build workflow. Existing MSVC consumers continue using prebuilt artifacts; generated Rust bindings and publishing integration remain separate.
GitOrigin-RevId: abd5049245aece90a116fc3bfeac2b158a76f6af
## Why
V8's Abseil and protobuf's shared Abseil can be built for different C++ runtimes. Give V8's copy a distinct inline namespace so both can link into one binary without interposing incompatible functions.
## What changed
- Move pinned V8 dependency imports and BUILD overlays into `third_party/v8`, and inject those repositories into V8 through a module-extension bridge with no fallback downloads.
- Build V8's Abseil with a V8-specific inline namespace while preserving protobuf's shared Abseil namespace.
- Apply V8's C++ runtime settings in the Abseil, Highway, and simdutf overlays, and remove the shared `rules_cc` patch.
- Document source dependency ownership and the version, checksum, and overlay review procedure for V8 upgrades.
GitOrigin-RevId: 2b8e3deed285559f8dd3324647cb4b81089f2f56
Sean Huang