fix: allow sam validate to look built template

[sriram-mv]

Which issue(s) does this change fix?

#2613

Why is this change necessary?

• sam validate only looks for current template.yaml which maybe out of date, if a build has been run.

How does it address the issue?

• Directly check for a built template.yaml if present, sam build generates this template.

What side effects does this change have?

• None

Checklist

• Add input/output type hints to new functions/methods
• Write design document (Do I need to write a design document?)
• Write unit tests
• Write/update functional tests
• Write/update integration tests
• make pr passes
• make update-reproducible-reqs if dependencies were changed
• Write documentation

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[jfuss]

@sriram-mv Is there any kind of tests we need to include for this?

[Rabadash8820]

Just came across this PR from aws/serverless-application-model#1907. Any updates? Also out of curiosity, what will be the intended functionality now if we run sam validate before sam build? Will build be run automatically, or will validate just fail with a more informative error message?

[Rabadash8820]

@sriram-mv Why was this PR closed without merging?

[sriram-mv]

@Rabadash8820 : #2892 looks to be related to this and was the reason it was closed, Let me re-open and investigate to ensure.

[jfuss]

This is solved by #2892, from my understanding. If this that is not the case, please open a new Issue, as the one linked by this PR is closed.

Closing