pipInstallHook: handle pipInstallFlags __structuredAttrs-agnostically

pkgs/development/interpreters/python/hooks/pip-install-hook.sh

@@ -1,17 +1,27 @@
 # Setup hook for pip.
-echo "Sourcing pip-install-hook"
+# shellcheck shell=bash
 
-declare -a pipInstallFlags
+echo "Sourcing pip-install-hook"
 
 pipInstallPhase() {
     echo "Executing pipInstallPhase"
     runHook preInstall
 
+    # shellcheck disable=SC2154
     mkdir -p "$out/@pythonSitePackages@"
     export PYTHONPATH="$out/@pythonSitePackages@:$PYTHONPATH"
 
+    local -a flagsArray=(
+        --no-index
+        --no-warn-script-location
+        --prefix="$out"
+        --no-cache
+    )
+    concatTo flagsArray pipInstallFlags
+
     pushd dist || return 1
-    @pythonInterpreter@ -m pip install ./*.whl --no-index --no-warn-script-location --prefix="$out" --no-cache $pipInstallFlags
+    echoCmd 'pip install flags' "${flagsArray[@]}"
+    @pythonInterpreter@ -m pip install ./*.whl "${flagsArray[@]}"
     popd || return 1
 
     runHook postInstall