linux: Partially revert "linux: drop hacky passing around of positions"

This partially reverts commit 845e340ed98ef6d8a5c5d7069663f2cd034e508a.

This re-introduces the `pos` juggling previous done.

The rationale used in the commit was:

> This is long obsolete since the versions are maintained in a JSON
> file now.

That is only accurate for `mainline`. Other in-tree kernels are
maintained in different ways. This led to a loss of information.

Before (cf3f5c4def3c):

```
nix-repl> linux_latest.meta.position
".../pkgs/os-specific/linux/kernel/mainline.nix:34"
nix-repl> linux_rpi0.meta.position
".../pkgs/os-specific/linux/kernel/linux-rpi.nix:20"

```

After (2fb006b87f04c):

```
nix-repl> linux_latest.meta.position
".../pkgs/os-specific/linux/kernel/build.nix:558"
nix-repl> linux_rpi0.meta.position
".../pkgs/os-specific/linux/kernel/build.nix:558"
```

This is also observable for out-of-tree kernels:

```
nix-repl> pkgs.linux_jovian.meta.position
".../Jovian-NixOS/pkgs/linux-jovian/default.nix:11"

nix-repl> :r # after updating the Nixpkgs input

nix-repl> pkgs.linux_jovian.meta.position
"/nix/store/xjjq52iwslhz6lbc621a31v0nfdhr5ks-source/pkgs/os-specific/linux/kernel/build.nix:558"
```

This also conveniently works around the root cause of an
`stdenv.mkDerivation`-based `pos` infrec regression when using the
kernel package version in a NixOS configuration to conditionally
apply kernel patches.

0 files changed, 0 insertions, 0 deletions