python3Packages.meson-python: consistently use -C in setup hook

pkgs/development/python-modules/meson-python/add-build-flags.sh

@@ -11,13 +11,15 @@ mesonPythonBuildFlagsHook() {
   appendToVar pypaBuildFlags "-Cbuild-dir=$mesonBuildDir"
   appendToVar pipBuildFlags "-Cbuild-dir=$mesonBuildDir"
 
-  # Add all of mesonFlags to -Csetup-args for pypa builds
+  # Add all of mesonFlags to `setup-args`
   local flagsArray=()
   concatTo flagsArray mesonFlags mesonFlagsArray
   for f in "${flagsArray[@]}"; do
     appendToVar pypaBuildFlags "-Csetup-args=$f"
-    # This requires pip>23.0.1, see: https://meson-python.readthedocs.io/en/latest/how-to-guides/config-settings.html
-    appendToVar pipBuildFlags "--config-settings=setup-args=$f"
+
+    # Using the same config key multiple times requires pip>=23.1, see:
+    # https://meson-python.readthedocs.io/en/latest/how-to-guides/config-settings.html
+    appendToVar pipBuildFlags "-Csetup-args=$f"
   done
 }