OK after running the build script for flext for the first time I get a config-mac-pd-gcc.txt file, but I do not see this other config.txt file to edit...?
Using flext 0.5.1 on iMac G5 10.4.8
Re-run the same build.sh script again to create it (you'll have to run build.sh several times). If in doubt, please post on flext list (or, if everything else fails, read the README included with flext).
Best wishes,
Ico