Clean up cross bootstrapping

For a long time, we've had `crossLibcStdenv`, `*Cross` libc attributes,
and `*bsdCross` pre-libc package sets. This was always bad because
having "cross" things is "not declarative": the naming doesn't reflect
what packages *need* but rather how we *provide* something. This is
ugly, and creates needless friction between cross and native building.

Now, almost all of these `*Cross` attributes are gone: just these are
kept:

- Glibc's and Musl's are kept, because those packages are widely used
  and I didn't want to risk changing the native builds of those at this
  time.

- generic `libcCross`, `theadsCross`, and friends, because these relate
  to the convolulted GCC bootstrap which still needs to be redone.

The BSD and obscure Linux or freestnanding libcs have conversely all
been made to use a new `stdenvNoLibc`, which is like the old
`crossLibcStdenv` except:

1. It usable for native and cross alike

2. It named according to what it *is* ("a standard environment without
   libc but with a C compiler"), rather than some non-compositional
   jargon ("the stdenv used for building libc when cross compiling",
   yuck).

I should have done this change long ago, but I was stymied because of
"infinite recursions". The problem was that in too many cases we are
overriding `stdenv` to *remove* things we don't need, and this risks
cyles since those more minimal stdenvs are used to build things in the
more maximal stdenvs.

The solution is to pass `stage.nix` `stdenvNoCC`, so we can override to
*build up* rather than *tear down*. For now, the full `stdenv` is also
passed, so I don't need to change the native bootstraps, but I can see
this changing as we make things more uniform and clean those up.

Finally, the BSDs also had to be cleaned up, since they have a few
pre-libc dependencies, demanding a systematic approach. I realized what
rhelmot did in 61202561d92cf1cd74532fcbd8b9d6662c5bc57b (specify what
packages just need `stdenvNoLibc`) is definitely the right approach for
this, and adjusted NetBSD and OpenBSD to likewise use it.

1 files changed, 3 insertions, 3 deletions

diff --git a/pkgs/os-specific/windows/default.nix b/pkgs/os-specific/windows/default.nix
index 234abcde16117..7b9bbcc52f791 100644
--- a/pkgs/os-specific/windows/default.nix
+++ b/pkgs/os-specific/windows/default.nix
@@ -1,5 +1,5 @@
 { lib, stdenv, buildPackages
-, newScope, overrideCC, crossLibcStdenv, libcCross
+, newScope, overrideCC, stdenvNoLibc, libcCross
 }:
 
 lib.makeScope newScope (self: with self; {
@@ -14,11 +14,11 @@ lib.makeScope newScope (self: with self; {
   mingw_runtime = mingwrt;
 
   mingw_w64 = callPackage ./mingw-w64 {
-    stdenv = crossLibcStdenv;
+    stdenv = stdenvNoLibc;
   };
 
   # FIXME untested with llvmPackages_16 was using llvmPackages_8
-  crossThreadsStdenv = overrideCC crossLibcStdenv
+  crossThreadsStdenv = overrideCC stdenvNoLibc
     (if stdenv.hostPlatform.useLLVM or false
      then buildPackages.llvmPackages.clangNoLibcxx
      else buildPackages.gccWithoutTargetLibc.override (old: {