stdenv: disable shellcheck rule SC2048

we use [*] to support structuredAttrs and non

In pkgs/stdenv/generic/setup.sh line 1542:
    for curPhase in ${phases[*]}; do
                    ^----------^ SC2048 (warning): Use "${array[@]}" (with quotes) to prevent whitespace problems.

pkgs/stdenv/generic/setup.sh

@@ -1,5 +1,5 @@
 # shellcheck shell=bash
-# shellcheck disable=1090,2154,2123,2034,2178
+# shellcheck disable=1090,2154,2123,2034,2178,2048
 __nixpkgs_setup_set_original=$-
 set -eu
 set -o pipefail