Set LANG=C.UTF-8 in Nix shell

[aherrmann]

This is to fix CI failures on run-tests -m failures, see #1117 (comment):

Failures:
--
  |  
  | tests/RunTests.hs:70:7:
  | 1) failures //tests/failures/transitive-deps:lib-dFailure
  | uncaught exception: IOException of type InvalidArgument
  | fd:15: hGetContents: invalid argument (invalid byte sequence)
  |  
  | To rerun use: --match "/failures///tests/failures/transitive-deps:lib-dFailure/"
  |  
  | tests/RunTests.hs:70:7:
  | 2) failures //tests/failures/transitive-deps:lib-cFailure
  | uncaught exception: IOException of type InvalidArgument
  | fd:15: hGetContents: invalid argument (invalid byte sequence)
  |  
  | To rerun use: --match "/failures///tests/failures/transitive-deps:lib-cFailure/"

That failure already exists on master since #1115 see CI runs #424 and #426. So, it seems to be unrelated to this PR.

[mboes]

@Profpatsch is C.utf8 an option here?

[aherrmann]

@mboes See #1099 which switched from en_US.UTF-8 to C.UTF-8.

[Profpatsch]

@Profpatsch is C.utf8 an option here?

yep, C.UTF8 is something that glibc added a while ago. You don’t need those pesky locale archives for basic UTF8 support now.

[Profpatsch]

We should set it on the socket inside of RunTests.hs

[Profpatsch]

On second thought, we don’t gain that much from it, so let’s do this.