hack: mount docker config on gha

[crazy-max]

relates to https://github.com/docker/buildx/actions/runs/11954989788/job/33326387756#step:7:311

=== FAIL: tests TestIntegration (6.56s)
    run.go:272: copied docker.io/moby/buildkit:latest to local mirror localhost:46659/moby/buildkit:buildx-stable-1
time="2024-11-21T14:15:54Z" level=info msg="trying next host - response was http.StatusNotFound" host="localhost:46659"
    run.go:321: 
        	Error Trace:	/src/vendor/github.com/moby/buildkit/util/testutil/integration/run.go:321
        	            				/usr/local/go/src/sync/once.go:76
        	            				/usr/local/go/src/sync/once.go:67
        	            				/src/vendor/github.com/moby/buildkit/util/testutil/integration/run.go:319
        	            				/src/vendor/github.com/moby/buildkit/util/testutil/integration/run.go:203
        	Error:      	Received unexpected error:
        	            	httpReadSeeker: failed open: unexpected status code https://registry-1.docker.io/v2/amd64/busybox/manifests/sha256:023917ec6a886d0e8e15f28fb543515a5fcd8d938edb091e8147db4efed388ee: 429 Too Many Requests - Server message: toomanyrequests: You have reached your pull rate limit. You may increase the limit by authenticating and upgrading: https://www.docker.com/increase-rate-limit
        	            	github.com/moby/buildkit/util/contentutil.CopyChain
        	            		/src/vendor/github.com/moby/buildkit/util/contentutil/copy.go:87
        	            	github.com/moby/buildkit/util/testutil/integration.copyImagesLocal
        	            		/src/vendor/github.com/moby/buildkit/util/testutil/integration/run.go:269
        	            	github.com/moby/buildkit/util/testutil/integration.runMirror
        	            		/src/vendor/github.com/moby/buildkit/util/testutil/integration/run.go:358
        	            	github.com/moby/buildkit/util/testutil/integration.Run.lazyMirrorRunnerFunc.func3.1
        	            		/src/vendor/github.com/moby/buildkit/util/testutil/integration/run.go:320
        	            	sync.(*Once).doSlow
        	            		/usr/local/go/src/sync/once.go:76
        	            	sync.(*Once).Do
        	            		/usr/local/go/src/sync/once.go:67
        	            	github.com/moby/buildkit/util/testutil/integration.Run.lazyMirrorRunnerFunc.func3
        	            		/src/vendor/github.com/moby/buildkit/util/testutil/integration/run.go:319
        	            	github.com/moby/buildkit/util/testutil/integration.Run.func2.1
        	            		/src/vendor/github.com/moby/buildkit/util/testutil/integration/run.go:203
        	            	testing.tRunner
        	            		/usr/local/go/src/testing/testing.go:1690
        	            	runtime.goexit
        	            		/usr/local/go/src/runtime/asm_amd64.s:1700
        	Test:       	TestIntegration