The win32 addon static-CRT switch enabled the static_link_msvcrt cc
feature, but audiopus_sys's bundled opus is built through the generated
CMake toolchain, which pinned CMAKE_MSVC_RUNTIME_LIBRARY=MultiThreadedDLL
(/MD) as authoritative under CMP0091 NEW. The opus objects could then
still emit /MD and pull VCRUNTIME140.dll / conflict with the static CRT
the rest of the addon links, leaving the outcome dependent on compile-
flag ordering.
Pin CMAKE_MSVC_RUNTIME_LIBRARY to MultiThreaded (static release /MT) in
the msvc toolchain.cmake so opus deterministically matches rustc's
+crt-static and the static_link_msvcrt feature.
Verified with a fully cold `bazel build //:natives-win32-x64-baseline`
(opus recompiled): the produced .node imports no VCRUNTIME140.dll and no
api-ms-win-crt-* — only core Windows system DLLs.
Fixes#8439