Disable ASM hashes on MSVC? #315
Description
As documented in RustCrypto/asm-hashes#17 and elsewhere, the crates in asm-hashes don't work on Windows MSVC targets. This is unfortunate, but it's understandable given that assembly is inherently difficult to port to all platforms.
However, it seems unnecessary that this detail leaks into the crates in the hashes repository. Would it make sense to use conditional compilation to force the software versions of hashes on MSVC, even when the asm feature is enabled? (There is already precedent for ignoring the asm feature flag when no assembly builds are available for the current platform.)
My use case is that I want to enable the asm feature to allow for faster performance on compatible platforms, but I don't want to completely break the build for Windows users. I'd be happy to create a PR if you think this is a reasonable change.