Build details link not displayed in experimental mode

[CrazyMax]

related to #2376 (comment)

Build details link is not displayed for a build that fails through controller: https://github.com/docker/buildx/actions/runs/8522265808/job/23342157852?pr=2376#step:7:771

FROM busybox
RUN exit 1

Works without experimental mode enabled:

$ docker buildx build .
#0 building with "default" instance using docker driver

#1 [internal] load build definition from Dockerfile
#1 transferring dockerfile: 61B done
#1 DONE 0.0s

#2 [internal] load metadata for docker.io/library/busybox:latest
#2 DONE 0.5s

#3 [internal] load .dockerignore
#3 transferring context: 2B done
#3 DONE 0.0s

#4 [1/2] FROM docker.io/library/busybox:latest@sha256:c3839dd800b9eb7603340509769c43e146a74c63dca3045a8e7dc8ee07e53966
#4 CACHED

#5 [2/2] RUN exit 1
#5 ERROR: process "/bin/sh -c exit 1" did not complete successfully: exit code: 1
------
 > [2/2] RUN exit 1:
------
Dockerfile:2
--------------------
   1 |     FROM busybox
   2 | >>> RUN exit 1
   3 |
--------------------
ERROR: failed to solve: process "/bin/sh -c exit 1" did not complete successfully: exit code: 1

View build details: docker-desktop://dashboard/build/default/default/vetboddpu4fpa38o97opuyj0a

But not displayed when enabled:

$ BUILDX_EXPERIMENTAL=1 docker buildx build .
#0 building with "default" instance using docker driver

#1 [internal] connecting to local controller
#1 DONE 0.0s

#2 [internal] load build definition from Dockerfile
#2 transferring dockerfile: 61B done
#2 DONE 0.1s

#3 [internal] load metadata for docker.io/library/busybox:latest
#3 ...

#4 [auth] library/busybox:pull token for registry-1.docker.io
#4 DONE 0.0s

#3 [internal] load metadata for docker.io/library/busybox:latest
#3 DONE 1.0s

#5 [internal] load .dockerignore
#5 transferring context: 2B done
#5 DONE 0.1s

#6 [1/2] FROM docker.io/library/busybox:latest@sha256:c3839dd800b9eb7603340509769c43e146a74c63dca3045a8e7dc8ee07e53966
#6 CACHED

#7 [2/2] RUN exit 1
#7 ERROR: process "/bin/sh -c exit 1" did not complete successfully: exit code: 1
------
 > [2/2] RUN exit 1:
------
Dockerfile:2
--------------------
   1 |     FROM busybox
   2 | >>> RUN exit 1
   3 |
--------------------
ERROR: process "/bin/sh -c exit 1" did not complete successfully: exit code: 1