gnu-config: enable strictDeps

it would be as simple as setting `strictDeps = true` and
`buildInputs = [ bashNonInteractive ]` except this package is used
during the bootstrap of `stdenv`: this method of manually patching
seems to be the least complex way to get correct behavior while
avoiding cyclic when deriving `stdenv` itself.

successfully built the following, from x86_64-linux:
- `gnu-config`
- `pkgsCross.aarch64-multiplatform.buildPackages.gnu-config` (equivalent)
- `pkgsCross.aarch64-multiplatform.gnu-config`
- `pkgsCross.musl32.gnu-config`
- `pkgsMusl.gnu-config`
- `pkgsStatic.gnu-config`
- `pkgsi686Linux.gnu-config`

successfully eval'd `gnu-config` for the following systems:
- `aarch64-darwin`
- `aarch64-freebsd`
- `aarch64-linux-musl`
- `aarch64-linux`
- `x86_64-cygwin`
- `x86_64-darwin`
- `x86_64-freebsd`
- `x86_64-linux-musl`
- `x86_64-linux`

pkgs/by-name/gn/gnu-config/package.nix

@@ -2,6 +2,7 @@
   lib,
   stdenv,
   fetchurl,
+  runtimeShell,
 }:
 
 # Note: this package is used for bootstrapping fetchurl, and thus
@@ -53,6 +54,19 @@ stdenv.mkDerivation {
     runHook postInstall
   '';
 
+  fixupPhase = ''
+    runHook preFixup
+    if [[ -z "''${dontPatchShebangs-}" ]]; then
+      substituteInPlace $out/config.guess \
+        --replace-fail '#! /bin/sh' '#!${runtimeShell}'
+      substituteInPlace $out/config.sub \
+        --replace-fail '#! /bin/sh' '#!${runtimeShell}'
+    fi
+    runHook postFixup
+  '';
+
+  strictDeps = true;
+
   meta = {
     description = "Attempt to guess a canonical system name";
     homepage = "https://savannah.gnu.org/projects/config";

pkgs/stdenv/darwin/default.nix

@@ -1069,7 +1069,7 @@ assert bootstrapTools.passthru.isFromBootstrapFiles or false; # sanity check
           )
           ++ lib.optionals localSystem.isAarch64 [
             prevStage.updateAutotoolsGnuConfigScriptsHook
-            prevStage.gnu-config
+            prevStage.updateAutotoolsGnuConfigScriptsHook.gnu_config
           ]
           ++ lib.optionals localSystem.isx86_64 [ prevStage.darwin.Csu ]
           ++ (with prevStage.darwin; [

pkgs/stdenv/linux/default.nix

@@ -875,7 +875,7 @@ assert bootstrapTools.passthru.isFromBootstrapFiles or false; # sanity check
           ++ lib.optionals (localSystem.libc == "musl") [ fortify-headers ]
           ++ [
             prevStage.updateAutotoolsGnuConfigScriptsHook
-            prevStage.gnu-config
+            prevStage.updateAutotoolsGnuConfigScriptsHook.gnu_config
           ]
           ++ [
             gcc-unwrapped.gmp

pkgs/top-level/all-packages.nix

@@ -287,7 +287,9 @@ with pkgs;
   updateAutotoolsGnuConfigScriptsHook = makeSetupHook {
     name = "update-autotools-gnu-config-scripts-hook";
     substitutions = {
-      gnu_config = gnu-config;
+      gnu_config = gnu-config.override {
+        runtimeShell = targetPackages.stdenv.shell;
+      };
     };
   } ../build-support/setup-hooks/update-autotools-gnu-config-scripts.sh;