ci: add MinGW build for Rust crate

[bnjbvr]

Investigating bytecodealliance/wasmtime#4003...

[bnjbvr]

Nice! It now shows the same mingw failure that we were seeing on wasmtime, with @abrown's patches from #56.

Would be nice if someone wanted to fix this upstream, please :)

[abrown]

Summary of this investigation for later reference: in bytecodealliance/wasmtime#4003 we discovered that the ittapi C code uses the uncommon strnlen_s function. On older versions of MinGW (GitHub runners currently come with v8.1.0 pre-installed), this function was not available. Since v8.1.0, other versions have been published; this re-installs MinGW with a recent version which includes strnlen_s. The special upgrade code in the GitHub workflow can be removed if/when MinGW is upgraded in all Windows GitHub runners: actions/runner-images#5530. This issue only really applies if someone builds the ittapi crate with --target x86_64-pc-windows-gnu, the MinGW target.

[bnjbvr]

Thanks for pushing this through, @abrown!