bake should not skip compose model normalization

[ndeloof]

closes #906

[crazy-max]

Looks like this test fails: https://github.com/docker/buildx/actions/runs/4989923431/jobs/8934490857?pr=1803#step:4:581

#17 67.71 === CONT  TestReadTargetsWithDotCompose
#17 67.71     bake_test.go:366: 
#17 67.71         	Error Trace:	/src/bake/bake_test.go:366
#17 67.71         	Error:      	Not equal: 
#17 67.71         	            	expected: "Dockerfile.webapp"
#17 67.71         	            	actual  : "Dockerfile"
#17 67.71         	            	
#17 67.71         	            	Diff:
#17 67.71         	            	--- Expected
#17 67.71         	            	+++ Actual
#17 67.71         	            	@@ -1 +1 @@
#17 67.71         	            	-Dockerfile.webapp
#17 67.71         	            	+Dockerfile
#17 67.71         	Test:       	TestReadTargetsWithDotCompose

I recall we needed to skip normalization to be able to merge compose files otherwise normalization overrides some fields.

[ndeloof]

@crazy-max looking at failing test I guess this is an issue we need to fix on Compose as well

[ndeloof]

I'm not sure I understand the fix covered by TestReadTargetsWithDotCompose. sanitizeTargetName to convert web.app with web_app then merge targets with same resulting name, while those were distinct in compose

[crazy-max]

I'm not sure I understand the fix covered by TestReadTargetsWithDotCompose. sanitizeTargetName to convert web.app with web_app then merge targets with same resulting name, while those were distinct in compose

Yes this is because compose service name can have invalid chars for a bake target:

buildx/bake/bake.go

Line 36 in f102ad7

validTargetNameChars = `[a-zA-Z0-9_-]+`

When merging both files with normalization I have:

{
          "web_app": {
            "context": ".",
            "dockerfile": "Dockerfile",
            "args": {
              "buildno": "1",
              "buildno2": "12"
            },
            "network": ""
          }
        }

Without

{
          "web_app": {
            "context": ".",
            "dockerfile": "Dockerfile.webapp",
            "args": {
              "buildno": "1",
              "buildno2": "12"
            },
            "network": ""
          }
        }

Seems because normalization does not left dockerfile empty and set it to Dockerfile which during merging use this one: https://github.com/compose-spec/compose-go/blob/f038655338287cfe5aa4b280363796eb6e7fc41e/loader/normalize.go#L51