Allow using pdm run to run a command not on PATH

[whitequark]

Is your feature request related to a problem? Please describe.

At the moment if I want to run a script with environment variables PDM_PROJECT_ROOT, VIRTUAL_ENV, or any from the _.env_file line in [tool.pdm.scripts] section in pyproject.toml, I cannot do this. E.g.:

$ pdm run ./build_top.sh
[PdmUsageError]: Command './build_top.sh' is not found in your PATH.

Describe the solution you'd like

It would be nice if PDM checked if the command is an absolute or relative path and ran it directly in that case, without a PATH lookup. I have no opinion on what to do if it's both a local file and a command on PATH; any of "display an error on conflict", "prefer one or the other", or "require the path to have at least one separator for the local command to run" (i.e. require pdm run ./build.sh and disallow pdm run build.sh) are fine with me.

[whitequark]

That was fast! Thanks so much, this will improve my workflow.