New review comment by yopito on void-packages repository

https://github.com/void-linux/void-packages/pull/26962#discussion_r565567642

Comment:
ah, thanks @sgn for reminding about pre_ stages.  
I had trouble to export variable `SHIBOKEN_CLANG_OPTIONS`, hence my quirk above ... 
fixed by use of `pre_build`, let's GH actions processing it again.