fix: bail if purs exits non-ok

[cakekindel]

closes #1284

Description of the change

TODO

Checklist:

• Added the change to the "Unreleased" section of the changelog
• Added some example of the new feature to the README
• Added a test for the contribution (if applicable)

P.S.: the above checks are not compulsory to get a change merged, so you may skip them. However, taking care of them will result in less work for the maintainers and will be much appreciated 😊

[cakekindel]

root@3a9a77b24532:/app# node ../spago/bin/bundle.js build
Reading Spago workspace configuration...

✓ Selecting 14 packages to build:
  ...
  
Downloading dependencies...
Building...
‼ Failed to decode PsaResult at index '0': Unexpected end of JSON input
Json was: 

✘ purs exited with non-ok status code: BySignal "SIGKILL"

[cakekindel]

hmm maybe dying isn't the right thing to do?

[f-f]

Uh, it looks like this uncovered a funny bug - CI is failing on this test, which should have never passed in the first place because we are supposed to fail in that condition

[f-f]

Having this code structured as a series of if/else makes it extra confusing, let's move it to a case statement, e.g.

case Array.all identity arrErrorsIsEmpty, Cmd.exitedOk result of
  -- No errors, and 0 exit code
  true, true -> ...
  -- No errors, but non-zero exit code, so something's up
  true, false -> ...
  -- Compilation errors, print them out
  false, _ -> ...

Let's also try to catch the JSON decoding error earlier: the scenario we are trying to prevent here has err being an empty string. So let's try to not print the warning if that's the case, hopefully it will reduce the log noise.

[cakekindel]

ok no problem, ended up changing the output traversal to collect into an array of eithers to defer that logging and changed to a case expression