don't print build details when progress is rawjson

[ndeloof]

when a build is ran using --progress=rawjson output should only contain line-delimited json stream
PrintBuildDetails to display an additional human-readable message at the end of the build breaks parsing this stream

Another option would be to use stdout for json and stderr for such messages

[crazy-max]

Looks good

Can you also add it to build command:

buildx/commands/build.go

Line 297 in d0177c6

if progressMode != progressui.QuietMode {

We might as well skip printing image id / digest in raw json mode:

buildx/commands/build.go

Line 300 in d0177c6

fmt.Println(getImageID(resp.ExporterResponse))

Also skip printing warnings with this mode:

buildx/commands/build.go

Line 756 in d0177c6

if len(warnings) == 0 || mode == progressui.QuietMode {

[crazy-max]

LGTM thanks