Hello, I'm in favor of merging Arnaud's patch for macOS while waiting for a better solution like relying on Grand Central Dispatch or another non-signal-based solution (https://github.com/php/php-src/pull/13468), which would allow max_execution_time to work with ZTS builds on mac as well.
I'm also in favor of using wall-clock time wherever possible (disclaimer: I'm the original author of this feature for Linux and FreeBSD). Best,