build: fix `--error-on-warn` for macOS

XCode builds on macOS do not appear to inherit the `cflags` setting.

Signed-off-by: Richard Lau <riclau@uk.ibm.com>

PR-URL: https://github.com/nodejs/node/pull/33357
Refs: https://github.com/nodejs/node/pull/32685


Reviewed-By: Michael Dawson <michael_dawson@ca.ibm.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Jiawen Geng <technicalcute@gmail.com>