nodeselector keyvalues are not parsed properly for kubernetes driver

[MichalAugustyn]

Issue description

Based on the docs, it should be possible to pass multiple nodeselector keyvalues using

nodeselector="label1=value1,label2=value2"

By quoting the nodeselector value, it should be parsed with this line becoming a list of keyvalues.

It seems that the second keyvalue, label2 in this case, is treated as another driver-opt rather than a keyvalue for nodeselector. It might be caused by the way driver-opts are parsed (using csvToMap func).

Reproducing the issue

$ docker buildx create --driver kubernetes --driver-opt replicas=1,nodeselector="kubernetes.io/arch=arm64,kubernetes.io/arch=arm" --use
unruffled_elion
$ touch Dockerfile
$ docker buildx build . 
[+] Building 0.0s (0/0)                                                                                                                                                                       
error: no valid drivers found: invalid driver option kubernetes.io/arch for driver kubernetes

[odinsy]

same problem here, multiple labels doesn't work

$ docker buildx create --use --bootstrap --name kube --driver=kubernetes --platform=linux/amd64 --node=builder-amd64 --driver-opt=namespace=gitlab,nodeselector="kubernetes.io/arch=amd64,app=gitlab-runner"
ERROR: failed to initialize builder kube (builder-amd64): invalid driver option app for driver kubernetes

buildx version

$ docker buildx version
github.com/docker/buildx v0.9.1 ed00243a0ce2a0aee75311b06e32d33b44729689