distro-build-manifest failure on Ubuntu 21.04

AGL build fails on Ubuntu 21.04 in distro-build-manifest with error

The problem seems to be due to snippet

in meta-agl/scripts/.aglsetup_genconfig.bash generates empty fragment

I have found that

fails in append_fragment.

Very similar problem is described here: https://github.com/containers/podman/issues/6659#issuecomment-661199469

Looks like bash creates temporary file for heredocs and passes fd to deleted file to command that use heredocs. Somehow this worked before...