containers: Fix out of tree builds for i386 unit-tests container
containers: Fix out of tree builds for i386 unit-tests container

This was using the wrong path in builddir instead of srcdir.

martinpitt/cockpit,SotolitoLabs/cockpit,Scribery/cockpit,cockpituous/cockpit,mareklibra/cockpit,stefwalter/cockpit,petervo/cockpit,stefwalter/cockpit,deryni/cockpit,martinpitt/cockpit,petervo/cockpit,mvollmer/cockpit,mvollmer/cockpit,Scribery/cockpit,petervo/cockpit,deryni/cockpit,garrett/cockpit,moraleslazaro/cockpit,SotolitoLabs/cockpit,Scribery/cockpit,moraleslazaro/cockpit,andreasn/cockpit,moraleslazaro/cockpit,stefwalter/cockpit,moraleslazaro/cockpit,cockpit-project/cockpit,moraleslazaro/cockpit,mvollmer/cockpit,SotolitoLabs/cockpit,andreasn/cockpit,mvollmer/cockpit,Scribery/cockpit,andreasn/cockpit,cockpit-project/cockpit,cockpituous/cockpit,petervo/cockpit,petervo/cockpit,garrett/cockpit,moraleslazaro/cockpit,andreasn/cockpit,SotolitoLabs/cockpit,mareklibra/cockpit,martinpitt/cockpit,andreasn/cockpit,mareklibra/cockpit,SotolitoLabs/cockpit,garrett/cockpit,stefwalter/cockpit,Scribery/cockpit,cockpit-project/cockpit,mareklibra/cockpit,petervo/cockpit,mareklibra/cockpit,cockpituous/cockpit,SotolitoLabs/cockpit,SotolitoLabs/cockpit,cockpituous/cockpit,cockpituous/cockpit,stefwalter/cockpit,mareklibra/cockpit,mareklibra/cockpit,martinpitt/cockpit,cockpit-project/cockpit,stefwalter/cockpit,cockpituous/cockpit,Scribery/cockpit,cockpit-project/cockpit,stefwalter/cockpit,garrett/cockpit,deryni/cockpit,garrett/cockpit,petervo/cockpit,deryni/cockpit,Scribery/cockpit,deryni/cockpit,mvollmer/cockpit,deryni/cockpit,martinpitt/cockpit,andreasn/cockpit,moraleslazaro/cockpit,deryni/cockpit,andreasn/cockpit