meson: Enable SSE4.1 for MSVC

Modern MSVC always supports compiling with the SSE4.1 intrinsics with
no additional command line options, but doesn't have any options for
auto-vectorizing into SSE4.1.

Reviewed-by: Erik Faye-Lund <>
Part-of: <!16840>
183 jobs for !16840 with sse4.1 in 48 minutes and 1 second (queued for 9 seconds)
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