[18.09] builder: set externalkey option for faster hook processing

[tonistiigi]

backport moby#38291

@thaJeztah @andrewhsu @tiborvass @fcrisciani

This is a regression in 18.09 as 18.06-experimental used host networking.

[fcrisciani]

LGTM

[thaJeztah]

LGTM

[andrewhsu]

LGTM on green

[thaJeztah]

PowerPC failing on a flaky test, but green otherwise;

19:10:47 FAIL: docker_api_swarm_test.go:296: DockerSwarmSuite.TestAPISwarmLeaderElection
19:10:47 
19:10:47 [da298174256e7] waiting for daemon to start
19:10:47 [da298174256e7] daemon started
19:10:47 
19:10:47 [d2376550a395d] waiting for daemon to start
19:10:47 [d2376550a395d] daemon started
19:10:47 
19:10:47 [d4ca5161effa7] waiting for daemon to start
19:10:47 [d4ca5161effa7] daemon started
19:10:47 
19:10:47 [da298174256e7] exiting daemon
19:10:47 assertion failed: error is not nil: Error response from daemon: rpc error: code = DeadlineExceeded desc = context deadline exceeded
19:10:47 [d2376550a395d] exiting daemon
19:10:47 [d4ca5161effa7] exiting daemon
```

[tonistiigi]

What are the build failures in windowsRS1? I don't see how it could be related to this PR and #122 was green. cc @tiborvass if this is related to moby/buildkit#661

Is the hang in janky the sign that containerd1.2 issue is back? @thaJeztah @andrewhsu

[thaJeztah]

Janky failures (docker-py) are;

19:55:19 _________________ ServiceTest.test_create_service_with_config __________________
19:55:19 /docker-py/tests/integration/api_service_test.py:632: in test_create_service_with_config
19:55:19     assert container is not None
19:55:19 E   AssertionError: assert None is not None
19:55:19 _________________ ServiceTest.test_create_service_with_secret __________________
19:55:19 /docker-py/tests/integration/api_service_test.py:580: in test_create_service_with_secret
19:55:19     assert container is not None
19:55:19 E   AssertionError: assert None is not None
19:55:19 === 2 failed, 326 passed, 5 skipped, 4 xfailed, 1 xpassed in 447.45 seconds ====
22:57:02 Build timed out (after 200 minutes). Marking the build as failed.
22:57:02 Build timed out (after 200 minutes). Marking the build as aborted.

Not sure if they're the same as before 😞

Windows failures are;

20:43:15 FAIL: docker_cli_build_test.go:3326: DockerSuite.TestBuildVerifySingleQuoteFails
20:43:15 
20:43:15 assertion failed: 
20:43:15 Command:  d:\CI\CI-73911117b3\binary\docker.exe run --rm testbuildsinglequotefails
20:43:15 ExitCode: 2
20:43:15 Error:    exit status 2
20:43:15 Stdout:   
20:43:15 Stderr:   [: '-c',: unknown operand
20:43:15 
20:43:15 
20:43:15 Failures:
20:43:15 ExitCode was 2 expected 127



20:45:43 ----------------------------------------------------------------------
20:45:43 FAIL: docker_cli_build_test.go:6048: DockerSuite.TestBuildWorkdirImageCmd
20:45:43 
20:45:43 docker_cli_build_test.go:6061:
20:45:43     c.Assert(strings.TrimSpace(out), checker.Equals, lookingFor)
20:45:43 ... obtained string = "[\"sh\"]"
20:45:43 ... expected string = "null"

I suspect we need to backport moby#38277 to fix that (we were using :latest in CI 😞

[tonistiigi]

@thaJeztah Do I include that in this PR to see if it goes green?

[thaJeztah]

opened #125, but you could rebase on top of that if you want to combine them