swift-corelibs: actually provide and use the hook

@emilazy found a bug in #234861 when building e2fsprogs in that the hook
is not actually applied, so e2fsprogs fails to have its rpath set and
fails to find CoreFoundation and crashes.

To fix the bug, copy the hook into CF’s `nix-support/setup-hook`. That
will cause the hook to be used by anything that requires it. To avoid
further churn to the previous stdenv, this commit requires the rework,
which has been written to build successfully while this hook is active.

pkgs/os-specific/darwin/swift-corelibs/corefoundation.nix

@@ -67,9 +67,10 @@ stdenv.mkDerivation {
   enableParallelBuilding = true;
 
   postInstall = ''
-    install_name_tool -id '@rpath/CoreFoundation.framework/Versions/A/CoreFoundation' \
+    install_name_tool -id "@rpath/CoreFoundation.framework/Versions/A/CoreFoundation" \
       "$out/Library/Frameworks/CoreFoundation.framework/Versions/A/CoreFoundation"
-  '';
 
-  darwinEnvHook = makeSetupHook { name = "darwin-env-hook"; } ./pure-corefoundation-hook.sh;
+    mkdir -p "$out/nix-support"
+    substituteAll ${./pure-corefoundation-hook.sh} "$out/nix-support/setup-hook"
+  '';
 }