If $INFORMIXDIR/lib/sqlexec does not have the correct permissions, I'd
suggest the correct fix is to run the installation script again

I usually find the way the INFORMIXDIR/lib/sqlexec has the wrong
permissions is that someone has copied the files from one machine to
another via tar or simialr.

If INFORMIXDIR/lib/sqlexec is incorrect then no doubt a number of
others will be incorrect too.