This makes the flow of data easier to understand. There's little downside
because the args in question are already inspected by the stdenvs.
cross-compiling in particular is simpler because we don't need to worry
about overriding the config closed over by `allPackages`.
This commit changes the dependencies of stdenv, and clean-up the stdenv
story by removing the `defaultStdenv` attribute as well as the `bootStdenv`
parameter.
Before, the final bootstrapping stage's stdenv was provided by
all-packages, which was iterating multiple times over the
top-level/default.nix expression, and non-final bootstrapping stages'
stdenvs were explicitly specified with the `bootStdenv` parameter.
Now, all stages' stdenvs are specified with the `stdenv` parameter.
For non-final bootstrapping stages, this is a small change---basically just
rename the parameter.
For the final stage, top-level/default.nix takes the chosen stdenv and
makes the final stage with it.
`allPackages` is used to make all bootstrapping stages, final and
non-final alike. It's basically the expression of `stage.nix` (along with a
few partially-applied default arguments)
Note, the make-bootstrap-tools scripts are temporarily broken
This ensures that most "trivial" derivations used to build NixOS
configurations no longer depend on GCC. For commands that do invoke
gcc, there is runCommandCC.
This change is not backward compatible, in the sense that this allow you to
override the packages which used to be overriden by the last stage of
stdenv. Note, this does not mean that these packages would be used by
stdenv.
This condition used to be implicit in the sense that the stdenvOverrides
uses pkgs_6, instead of pkgs_7 as its super set, and also that each stage of
the compiler is build again the bootstrap packages of the previous stage,
thus overriden by the stdenv.override function.
