Simplify definitions of libcs

- Used `stdenvNoLibc` directly in the package files instead of
  overriding `stdenv` to it in `all-packages.nix`
- Moved applicable libcs to `pkgs/by-name` (note: not newlib because
  it's also accessible via `newlib-nano`)

pkgs/by-name/av/avrlibc/package.nix

@@ -1,12 +1,12 @@
 {
   lib,
-  stdenv,
+  stdenvNoLibc,
   fetchurl,
   automake,
   autoconf,
 }:
 
-stdenv.mkDerivation (finalAttrs: {
+stdenvNoLibc.mkDerivation (finalAttrs: {
   pname = "avr-libc";
   version = "2.2.1";
 

pkgs/by-name/mu/musl/package.nix

@@ -1,11 +1,17 @@
 {
   stdenv,
+  stdenvNoLibc,
   lib,
   fetchurl,
   linuxHeaders ? null,
   useBSDCompatHeaders ? true,
 }:
 let
+  stdenv' = if stdenv.hostPlatform != stdenv.buildPlatform then stdenvNoLibc else stdenv;
+in
+let
+  stdenv = stdenv';
+
   cdefs_h = fetchurl {
     name = "sys-cdefs.h";
     url = "https://git.alpinelinux.org/aports/plain/main/libc-dev/sys-cdefs.h?id=7ca0ed62d4c0d713d9c7dd5b9a077fba78bce578";

pkgs/by-name/wa/wasilibc/package.nix

@@ -1,7 +1,6 @@
 {
-  stdenv,
+  stdenvNoLibc,
   buildPackages,
-  fetchFromGitHub,
   lib,
   firefox-unwrapped,
   firefox-esr-unwrapped,
@@ -11,7 +10,7 @@ let
   pname = "wasilibc";
   version = "22-unstable-2024-10-16";
 in
-stdenv.mkDerivation {
+stdenvNoLibc.mkDerivation {
   inherit pname version;
 
   src = buildPackages.fetchFromGitHub {

pkgs/development/misc/newlib/default.nix

@@ -1,5 +1,5 @@
 {
-  stdenv,
+  stdenvNoLibc,
   fetchurl,
   buildPackages,
   lib,
@@ -11,7 +11,7 @@
   nanoizeNewlib ? false,
 }:
 
-stdenv.mkDerivation (finalAttrs: {
+stdenvNoLibc.mkDerivation (finalAttrs: {
   pname = "newlib";
   version = "4.5.0.20241231";
 
@@ -76,7 +76,7 @@ stdenv.mkDerivation (finalAttrs: {
     # "normal" view to the outside world: the binaries in $out will
     # execute on `stdenv.hostPlatform`.  We then fool newlib's build
     # process into doing the right thing.
-    "--host=${stdenv.targetPlatform.config}"
+    "--host=${stdenvNoLibc.targetPlatform.config}"
 
   ]
   ++ (
@@ -134,8 +134,8 @@ stdenv.mkDerivation (finalAttrs: {
     + ''[ "$(find $out -type f | wc -l)" -gt 0 ] || (echo '$out is empty' 1>&2 && exit 1)'';
 
   passthru = {
-    incdir = "/${stdenv.targetPlatform.config}/include";
-    libdir = "/${stdenv.targetPlatform.config}/lib";
+    incdir = "/${stdenvNoLibc.targetPlatform.config}/include";
+    libdir = "/${stdenvNoLibc.targetPlatform.config}/lib";
   };
 
   meta = with lib; {

pkgs/top-level/all-packages.nix

@@ -6646,10 +6646,6 @@ with pkgs;
 
   h3 = h3_3;
 
-  avrlibc = callPackage ../development/misc/avr/libc {
-    stdenv = stdenvNoLibc;
-  };
-
   sourceFromHead = callPackage ../build-support/source-from-head-fun.nix { };
 
   jruby = callPackage ../development/interpreters/jruby { };
@@ -8005,12 +8001,6 @@ with pkgs;
     withGd = true;
   };
 
-  musl = callPackage ../by-name/mu/musl/package.nix (
-    lib.optionalAttrs (stdenv.hostPlatform != stdenv.buildPlatform) {
-      stdenv = stdenvNoLibc;
-    }
-  );
-
   # These are used when building compiler-rt / libgcc, prior to building libc.
   preLibcHeaders =
     let
@@ -8082,10 +8072,6 @@ with pkgs;
         package = windows.mcfgthreads;
       };
 
-  wasilibc = callPackage ../development/libraries/wasilibc {
-    stdenv = stdenvNoLibc;
-  };
-
   # Only supported on Linux and only on glibc
   glibcLocales =
     if stdenv.hostPlatform.isLinux && stdenv.hostPlatform.isGnu then
@@ -16287,12 +16273,9 @@ with pkgs;
 
   xp-pen-deco-01-v2-driver = libsForQt5.xp-pen-deco-01-v2-driver;
 
-  newlib = callPackage ../development/misc/newlib {
-    stdenv = stdenvNoLibc;
-  };
+  newlib = callPackage ../development/misc/newlib { };
 
   newlib-nano = callPackage ../development/misc/newlib {
-    stdenv = stdenvNoLibc;
     nanoizeNewlib = true;
   };