Testing use of krb5 and gssapi in PostgreSQL?

[Stephan Bergmann]

The only use of WITH_KRB5 and WITH_GSSAPI in LO appears to be the 
PostgreSQL support (see connectivity/Library_postgresql-sdbc-impl.mk and 
external/postgresql/ExternalProject_postgresql.mk).  Is there some 
documentation how to test whether the use of krb5 and gssapi in the 
PostgreSQL support actually works?

(Asking because the latest Flatpak runtime org.freedesktop.Sdk//19.08 
dropped krb5, and I wonder whether I should bundle it in the LO 
Flatpak---but without even knowing how to test that it will actually 
works as intended, or just configure the Flatpak build --without-krb5 
--without-gssapi.)