New comment by pullmoll on void-packages repository

https://github.com/void-linux/void-packages/issues/27437#issuecomment-751386078

Comment:
Thank you @newbluemoon for looking into it. Your stream edits work better than my hack and I'll use that in 98-fixup-gir-path.sh for now.

Slightly modified to only stream edit if any files contain the `INTROSPECTION_{GIR,TYPLIB}DIR`, or otherwise `sed` would error out.