Updates tests for testers.testEqualContents with diffoscope and fixes
some bugs in tests (e.g. fileDiff always succeed because subshell does
not inherit errexit option).
Closes#193336Closes#261694
Related to #108984
The goal here was to get the following flake to build and run on
`aarch64-darwin`:
```nix
{ inputs.nixpkgs.url = <this branch>;
outputs = { nixpkgs, ... }: {
checks.aarch64-darwin.default =
nixpkgs.legacyPackages.aarch64-darwin.nixosTest {
name = "test";
nodes.machine = { };
testScript = "";
};
};
}
```
… and after this change it does. There's no longer a need for the
user to set `nodes.*.nixpkgs.pkgs` or
`nodes.*.virtualisation.host.pkgs` as the correct values are inferred
from the host system.
This is very useful in conjunction with meta.pkgConfigModules, as the
new tester can use the list provided by this meta attribute as a default
value for moduleNames, making its usage in passthru.tests very
convenient.
For backwards compatibility, a shim under the old name is maintained
with a warning.
the output made me think that the test failed but did not fail
testBuildFailure-helloDoesNotFail> Checking /nix/store/x6403x1llpk00i59cmr96iy92mx1f7hb-hello-2.12.1/testBuildFailure.log
testBuildFailure-helloDoesNotFail> testBuildFailure: The builder did not fail, but a failure was expected!
