Only pass .asm files to masm

[thomcc]

This changes the handling of assembly on MSVC targets so that only .asm files are passed to masm. This is more in line with how things were handled in cc <1.0.77, and would have avoided #754.

[ChrisDenton]

Effectively restoring the previous behaviour to prevent unintentional breakages looks good to me. I only have a few minor nits.

[ChrisDenton]

LGTM, thanks!

[MarijnS95]

and would have avoided #754.

Fwiw this is more-so caused by the zstd-sys build script looking at host OS rather than target OS, while cross-compiling. However, it seems that its choice to include this file comes down to compiler support, so if the cross-compiler was having clang-cl available that might explain why it was previously building fine.

[thomcc]

Fwiw this is more-so caused by the zstd-sys build script looking at host OS rather than target OS, while cross-compiling.

Yeah, the point is more: you should actually be allowed to compile that file with clang-cl, even if the logic you used to decide whether or not to include it was buggy.

[MarijnS95]

@thomcc is this still on track to be released? We're currently failing to compile tract-linalg because it detects ml64.exe isn't available and passes .S files to cc, which ends up invoking ml64.exe anyway.

https://github.com/sonos/tract/blob/main/linalg/build.rs

[thomcc]

Ah, thanks for the reminder, I'll do a release as soon as possible.

[thomcc]

@MarijnS95 Sorry for the delay, it's in https://github.com/rust-lang/cc-rs/releases/tag/1.0.78.

[thomcc]

A wrinkle here is that meson projects are expected to use .asm file as the file extension, regardless of assembler. I wonder if this will cause issues for us...

[ChrisDenton]

Oh hm. Maybe! We probably should have ways to override any and all heuristics in any case.