macOS: apply stack size increase for G'MIC

This MR is meant to try and alleviate https://github.com/c-koi/gmic-qt/issues/160 . (I haven't yet heard how the reporter triggers the stack exhaustion, though.)

I cannot test this code because Xcode no longer fits in my machine, so I'd love it if @ivany could check this.

Test Plan

Build Krita in macOS. Check that G'MIC filters do not crash.

Formalities Checklist

• I confirmed this builds.
• I confirmed Krita ran and the relevant functions work.
• I tested the relevant unit tests and can confirm they are not broken. (If not possible, don't hesitate to ask for help!)
• I made sure my commits build individually and have good descriptions as per KDE guidelines.
• I made sure my code conforms to the standards set in the HACKING file.
• I can confirm the code is licensed and attributed appropriately, and that unattributed code is mine, as per KDE Licensing Policy.