cross compilation broken if part contains 'uname'

[Ondrej Kubik]

Setup:
  snapcraft version: snapcraft 2.42.1 1594
  running inside lxd container on xenial
  cross compiling for armhhf
  part using nil plugin, only has stage-packages defined
  part has coreutils as stage package

Build:
  build fails when snapcraft wrongly executes uname from part instead of uname from host system

output:
Building part-name
/home/ubuntu/host/project/parts/part-name/install/bin/uname: 1: /home/ubuntu/host/project/parts/part-name/install/bin/uname: Syntax error: word unexpected (expecting ")")
Failed to run 'uname -srvmpio': Exited with code 2.

[Ondrej Kubik (ondrak)]

putting absolute path into snapcraft/internal/pluginhandler/__init__.py
fixes the problem

[Kyle Fazzari (kyrofa)]

Fix proposed here: https://github.com/snapcore/snapcraft/pull/2177 . Can you confirm that it works, Ondrej?

[Ondrej Kubik (ondrak)]

hmm, more trouble with similar thing:

/home/ubuntu/host/kura/stage/bin/uname: 1: /home/ubuntu/host/kura/stage/bin/uname: Syntax error: word unexpected (expecting ")")
/home/ubuntu/host/kura/stage/bin/ls: 1: /home/ubuntu/host/kura/stage/bin/ls: Syntax error: word unexpected (expecting ")")
/home/ubuntu/host/kura/stage/usr/bin/expr: 1: /home/ubuntu/host/kura/stage/usr/bin/expr: Syntax error: word unexpected (expecting ")")
/home/ubuntu/host/kura/stage/usr/bin/expr: 1: /home/ubuntu/host/kura/stage/usr/bin/expr: Syntax error: word unexpected (expecting ")")
/home/ubuntu/host/kura/stage/usr/bin/dirname: 1: /home/ubuntu/host/kura/stage/usr/bin/dirname: Syntax error: word unexpected (expecting ")")
/home/ubuntu/host/kura/stage/usr/bin/dirname: 1: /home/ubuntu/host/kura/stage/usr/bin/dirname: Syntax error: word unexpected (expecting ")")

I'm trying to rebuild part, while there are already in stage executables from other parts. But those executables are for different architecture. Part is build with maven, so I assume maven calls those utils, and because path points to stage in first place, it picks one for wrong arch.
I guess one way around is to change order of parts here but looks like something quite fragile when cross compiling.

So as start, I'd suggest that when we cross compile, we should not populate PATH like this, as that is destined to fail

Same can happen if I will have same tools but with different behaviour in my snap...but that could be probably considered as corner case