[minor] --path: silently gives wrong results with relative paths

[timotheecour]

--path doesn't work well when given a relative path in some cases at least; eg --path:. (or --path:compiler/..) fails below (down the line, not immediately) whereas --path:$(pwd) (or using explicit absolute path) works

Example

• create /mypathto/extend_aux.nim containing:

import std/nre
import compiler/ast

• add import extend_aux at the end of ./compiler/nim.nim in nim sources (for example at latest devel, b67dea7)

• recompile nim as follows:

 bin/nim c --skipUserCfg -o:/tmp/nim --stylecheck:off --path:/mypathto/ --noNimblePath --path:. compiler/nim.nim

fails with --path:.
fails with other equivalent relative paths eg --path:compiler/..
works with equivalent absolute path eg --path:$(pwd)

Current Output

/Users/timothee/git_clone/nim/Nim_devel/lib/impure/nre.nim(351, 27) Error: undeclared identifier: 'none'

Expected Output

works

Additional Information

D20191228T161300
at nim devel b67dea7

[metagn]

Maybe #22065 has mitigated this? Above instructions are very cumbersome, can't tell what the problem is at a glance