* Tests: Dockerfile: Change base to nimlang/nim:latest.
* Tests: Dockerfile: Remove unnecessary deps covered in the base image.
* Tests: Dockerfile: Replace manual cleanup with apt-get dist-clean.
* Tests: Dockerfile: Remove Nim installation step covered in the base image.
* Tests: Dockerfile: Remove cmake from deps.
* Tests: Dockerfile: Replace manual libplum building with nimble task.
* Build libplum without cmake.
* Use {.compile.} to compile libplum as part of tha package; remove separate build task.
* Rewrite flags construction, pass flags to compile, remove passC.
* Add localPassC.
* Combine libplum units to libplum_units.c.
* Tests: Dockerfile: Add the units file to the image.
* Add missing flags.
* CI: Remove redundant cmake invocations.
* Remove redundant nimble task invocation.
