x/dashboard: request for updated C compilers on windows builders

[thanm]

While working on issue #39326, I noticed that the C compilers we have installed on our windows builders (at least the ones I have used via gomote) are pretty ancient -- GCC 5.

It would be great if we could update the version to something a bit more recent (V10 maybe). Also worth noting that many folks are now using clang instead of gcc on windows -- it would be very helpful if our windows builders had clang installed as well.

[thanm]

@golang/release

[ALTree]

This is #35006.

I've been using the toolchain recommended in #35006 (comment) and it works much better than mingw. It's also completely static and requires no installation.

[thanm]

@ALTree thanks, that's helpful. I'll maybe try the musl.cc copy and see if I can make progress with that.

[thanm]

The toolchain from musl.cc helped a lot -- I was able to develop a fix for my lld bug using that.

I tried running all.bash on a windows gomote with the musl.cc toolchain (overriding the default gomote toolchain). There were a couple of failures of the form

    nm_test.go:121: building test executable failed: exit status 2 # command-line-arguments
        c:/workdir/x86_64-w64-mingw32-native/bin/../lib/gcc/x86_64-w64-mingw32/9.3.1/../../../libmsvcrt.a(/2203): duplicate symbol reference: _unlock_file in both libgcc(.text) and libgcc(.data)
        libgcc(.text): relocation target ___chkstk_ms not defined
        libgcc(.text): relocation target atexit not defined

This is with internal linking. Might be worth poking at those to see if they can be worked around, since other than that it looked good to me.

[bcmills]

Duplicate of #35006