builder: have TestBuildDockerignoringBadExclusion pass with buildkit

Signed-off-by: Tibor Vass <tibor@docker.com>
Upstream-commit: 9cc49b4ab91d1083932b952dec7475c46732b5b5
Component: engine

components/engine/integration-cli/docker_cli_build_test.go

@@ -2534,7 +2534,7 @@ func (s *DockerSuite) TestBuildDockerignoringBadExclusion(c *check.C) {
 		build.WithFile(".dockerignore", "!\n"),
 	)).Assert(c, icmd.Expected{
 		ExitCode: 1,
-		Err:      "error checking context: 'illegal exclusion pattern: \"!\"",
+		Err:      `: illegal exclusion pattern: "!"`,
 	})
 }