Client built with 'gcc -m32 -lodbc' is able to connect to PostgreSQL server with default unixODBC.i686 when the postgresql-odbc.i686 package is manually installed e.g. from koji build [1]. So the resolution of this bug is to make sure that the postgresql-odbc is categorized as multilib. [1] https://koji.fedoraproject.org/koji/buildinfo?buildID=811374
I was told this requires ticket against pungi-fedora: https://pagure.io/pungi-fedora/issue/124
This bug appears to have been reported against 'rawhide' during the Fedora 26 development cycle. Changing version to '26'.
Original ticket is resolved. I was able to install both postgresql-odbc.{i686,x86_64} into mock f27.