treewide: improve prepending and appending derivation arguments in bash code

Those would be problematic with __structuredAttrs turned on, because
they'd turn those nice bash arrays back into strings - and potentially
lose some of the values on the way.

pkgs/development/interpreters/python/hooks/python-catch-conflicts-hook-tests.nix

@@ -83,7 +83,7 @@ in {
     generatePythonPackage {
       pname = "cyclic-dependencies";
       preFixup = ''
-        propagatedBuildInputs+=("$out")
+        appendToVar propagatedBuildInputs "$out"
       '';
     };