A little shim derivation to get this header for Darwin, where it is
needed for cross compilation.
There's no real reason to do glibc and musl like that, but as I'm
maintaining it I suppose I can go overboard like that.
Intuitively, one cares mainly about the host platform: Platforms differ
in meaningful ways but compilation is morally a pure process and
probably doesn't care, or those difference are already abstracted away.
@Dezgeg also empirically confirmed that > 95% of checks are indeed of
the host platform.
Yet these attributes in the old cross infrastructure were defined to be
the build platform, for expediency. And this was never before changed.
(For native builds build and host coincide, so it isn't clear what the
intention was.)
Fixing this doesn't affect native builds, since again they coincide. It
also doesn't affect cross builds of anything in Nixpkgs, as these are no
longer used. It could affect external cross builds, but I deem that
unlikely as anyone thinking about cross would use more explicit
attributes for clarity, all the more so because the rarity of inspecting
the build platform.
I don't know when we can/should remove them, but this at least gets
people to stop using them. The preferred alternatives also date back to
17.09 so writing forward-compatable code without extra conditions is
easy.
Beginning with these as they are the least controversial.
Derivations where drawing their `system` attribute from `hostPlatform`
instead of `buildPlatform`. Fix that, and add an explanatory commment.
Fixes#45993
This, apparently, is not an official release (it's tagged, but the tarball is not
available on the official site), but this repo is the official repo mentioned on
the official site.
This fixes a bunch of very annoying bugs present in 0.99.4, e.g.
```
$ FBReader filename
```
does not crash anymore. Yay!
