How to override assembler?

[Andrew Katson]

I am working on Openssl for Bazel on Windows. 

I am running into an issue with the assembler. By default, Openssl uses nasm with MSVC but Bazel uses masm with MSVC. Openssl technically supports masm with MSVC too but the file comments say it is experimental and prod builds shouldn't rely on it. Is there any way to override the assembler used by the default x86_64 MSVC toolchain? 

I assume I could define my own toolchain but is there an existing one or way I could do this? 

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Andrew Katson