please_pex is dynamically linked

It shouldn't be, we aim to statically link our Go binaries to reduce incompatibility. 

See e.g. https://app.circleci.com/pipelines/github/thought-machine/please/6886/workflows/808db19f-2aa1-444c-b33e-11050c8df9fe/jobs/54396 for a case where it fails (yes, the image is Focal which is old now but it is still supported by Canonical, we should be able to run there too)