driver: add npipe url scheme support

[iankingori]

Buildkit on windows exposes an npipe endpoint (npipe:////./pipe/buildkitd) which can be used to create a remote builder for WCOW.

Testing this with a simple docker file gives the result below:

[jedevc]

Hm, yeah, this has always been valid!

LGTM, thanks! 🎉

[profnandaa]

Good catch, thanks!

[tianon-sso]

I'm trying to test this out with buildkit 0.13.0-rc2 and I think I must be holding it wrong (or maybe this PR wasn't enough? I believe the above screenshot says otherwise 😅)

I've got buildkitd.exe running successfully on my host, and I've got buildctl.exe successfully connecting to it, but when I try to run buildx 0.13.0-rc1 connected to it via buildx create --name windows --driver remote npipe:////./pipe/buildkitd, all subsequent commands then fail to connect and I'm at a loss for understanding why. 🙈

$ ~/Downloads/buildkit/buildctl.exe du
ID      RECLAIMABLE     SIZE    LAST ACCESSED
Reclaimable:    0B
Total:          0B

$ ~/Downloads/buildx-v0.13.0-rc1.windows-amd64.exe create --name windows --driver remote npipe:////./pipe/buildkitd
windows

$ ~/Downloads/buildx-v0.13.0-rc1.windows-amd64.exe --builder windows du
ERROR: failed to call diskusage: Unavailable: connection error: desc = "transport: Error while dialing: dial npipe: unknown network npipe"

Any clues as to what I've missed? Maybe I've misunderstood this PR entirely? 😂 ❤️ 🙇

[iankingori]

@tianon-sso this is interesting, appears to be a regression between when I checked in the code and now. I've tested using my previous buildx binary in docker and the rc. I'll put up a fix and add tests to catch this next time

[iankingori]

Seems this PR changed the remote driver to use dialer which doesn't support npipes. Trying to see whether we can use DialPipe from go winio