Add -trimpath to GoModulesBuilder

[scrofungulus]

This PR addresses the issue described here in the AWS SAM CLI repository.

Description of changes:
Adds a trim_go_path option to the GoModulesBuilder. Directly from the go help build command from the Go CLI:

-trimpath
                remove all file system paths from the resulting executable.
		Instead of absolute file system paths, the recorded file names
		will begin either a module path@version (when using modules),
		or a plain import path (when using the standard library, or GOPATH).

Ultimately, this addresses an issue that occurs when using sam build. Without -trimpath the compiled binaries computed hashes are different each time forcing CloudFormation to redeploy a Lambda function without code changes.

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

[sriram-mv]

Overall, this looks good. These options will need to be passed in from AWS SAM CLI as well here: https://github.com/aws/aws-sam-cli/blob/develop/samcli/lib/build/app_builder.py#L715

[sriram-mv]

I am happy to approve with a small test change.

[sriram-mv]

Can we add a test to show the difference between when trim path is enabled vs not enabled?

[scrofungulus]

@sriram-mv @mndeveci I have added this test case. I wrote a utility that will return the md5 hexdigest of the built binaries. I created a copy of the no-deps go project in testdata. By building an exact copy of that project with -trimpath enabled we can assert that their md5 hex digests are the same. Similarly, we can assert that they will not be equal without the -trimpath flag. This was the most straightforward way that I could think of. Hopefully it is sufficient.

[mndeveci]

Thanks for your contribution! I think changes looks good to me. Can we add an intergration test to validate this case? Integration test file can be found here; https://github.com/aws/aws-lambda-builders/blob/develop/tests/integration/workflows/go_modules/test_go.py#L18

[sriram-mv]

Thanks for making the changes!

[mndeveci]

Thanks for your contribution, looks good to me as well!

[sriram-mv]

@scrofungulus to use this effectively, the next step is to make changes in AWS SAM CLI as well. since it passes in the options based on the builder that is chosen. Those changes are showcased here: https://github.com/aws/aws-sam-cli/blob/develop/samcli/lib/build/app_builder.py#L714

Would you be open to contributing those changes there as well?

[scrofungulus]

@sriram-mv I'm definitely open to contributing! Looks straightforward.

[scrofungulus]

@sriram-mv pull request number 4300 addresses your above comment! 😃