libopus ships per-file SSE4.1 / SSSE3 C sources (opus/silk/x86/NSQ_del_dec_sse4_1.c
etc.) that assume the compiler picks up `-msse4.1` / `-mssse3` as per-file
CMake COMPILE_FLAGS. With clang-cl those bare -m flags are silently dropped,
so _mm_cvtepi16_epi32 + friends fail compile with 'always_inline function
requires target feature sse4.1, but would be inlined into a function that
is compiled without support for sse4.1'.
Workaround: set CFLAGS_x86_64_pc_windows_msvc + CXXFLAGS_x86_64_pc_windows_msvc
to `/clang:-msse4.1 /clang:-mssse3 /clang:-msse3 /clang:-msse2` before running
cargo xwin build. Every x86_64 Windows CPU shipped since 2008 has these
instruction sets so globally enabling them on this target is safe.
Also bump the tail -30 on cargo xwin output to tail -50 so the actual
compiler errors (not just the cmake wrapper panic) make it into the
ntfy / remote log file next time.
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