fix: Resolve symlinks on local invoke only

[valerena]

SAM CLI shouldn't be mounting symlinks by default when building in a container

Which issue(s) does this change fix?

Why is this change necessary?

Symbolic links are used in SAM CLI to achieve faster build times with build-in-source. The build process creates symlinks for dependencies, that then can be used when running sam local invoke. These symlinks don't need to be mounted during sam build.

How does it address the issue?

We add a new context property for the container to make a different decision depending on the context.

What side effects does this change have?

If SAM CLI users were relying on this behavior during builds, their workflow might get broken. Please create an issue if you're affected by this change, and we'll prioritize to add a new property to allow mounting symlinks in any case.

Mandatory Checklist

PRs will only be reviewed after checklist is complete

• Add input/output type hints to new functions/methods
• Write design document if needed (Do I need to write a design document?)
• Write/update unit tests
• Write/update integration tests
• Write/update functional tests if needed
• 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.

[seshubaws]

nit: samcli but not a blocker

[roger-zhangg]

LGTM