Revert "Merge pull request #1440 from buildkite/resolve-absolute-agent-path"
Revert "Merge pull request #1440 from buildkite/resolve-absolute-agent-path"

This reverts PR #1440. As discussed in the comments of that PR we found
it introduced a new issue and we'd like some more time to evaluate the
best response without holding up releasing 3.30.0

buildkite/agent,buildkite/agent,buildkite/agent