Add workaround for assembling crypto instructions on arm

[yuvald-sweet-security]

Hello,

This is a workaround for Zig issue ziglang/zig#10411 which prevents building the sha1-asm crate on zigbuild.

The end result is that in the special case that the ARMv8 crypto IS extension is requested the zig cc invocation turns from:
zig cc -g -target aarch64-linux-gnu ... -c src/aarch64.S -march=generic+crypto
to
zig cc -g -target aarch64-linux-gnu ... -c src/aarch64.S -march=generic+crypto -Xassembler -march=armv8-a+crypto

This way we skip zig cc and pass the correct march flag to clang-as directly. This solves #149.

As I'm not familiar with this codebase, the best way I found to implement this is to modify filter_linker_arg to return a vector of arguments. If there's another way you'd like me to structure this change please let me know.

[messense]

LGTM, thanks!