On Darwin, launchd may attempt to start agents before the Nix store is
mounted and available. This leads to failures when the agent's executable
or arguments reside in the Nix store.
This change wraps the agent's command in a shell script that uses
/bin/wait4path to ensure /nix/store is ready before executing the
original program. It also ensures that ProgramArguments are correctly
escaped and concatenated.
Instead of having to manually stub packages that should not be
downloaded we instead automatically stub all packages (except a small
list of whitelisted ones). Tests can re-introduce the real package by
using the `realPkgs` module argument.
systemd rejects the service unit due to whitespace in the environment
variable assignment, pointing to the repo path, being invalid for
systemd's unit format.
See https://github.com/nix-community/home-manager/issues/6023 for
details.
The git-sync variable should also be escaped due to similar issues
with e.g. local git urls.
Setting `outputSpecified` prevents `getOutput` from descending into
outputs, which don't have an overridden `outPath`.
Additionally, use `__spliced` to permit derivations to use the dummy as
an input.
This option provides a more convenient way to overlay dummy packages.
It also adds a function `config.lib.test.mkStubPackage` that can,
e.g., be used for `package` options.
