Trouble integrating #134

[kevinburkesegment]

First off, thank you very much for implementing this change, and for responding to public feedback.

I tried implementing this on my project, and basically as I understand it, an AWS profile must be loaded from a file on disk. This is where I ran into trouble - to load from disk basically means the file needs to be somewhere on the underlying host.

Alternatively, I could run my own plugin in the build pipeline, before the cache plugin, that writes the profile file to disk, and sets AWS_PROFILE_FILE or whatever the variable is named. But this sort of defeats the purpose of the cache buildkite plugin.

This is why we implemented it as an assume-role call with the role ARN being the variable - it's possible for us to put the role in environment variable in a way it's not possible to do with profile like this.