E build-depends-indep-without-arch-indep

The control file specifies source relations for architecture-independent packages, but no architecture-independent packages are built.

Refer to Debian Policy Manual section 7.7 (Relationships between source and binary packages - Build-Depends, Build-Depends-Indep, Build-Depends-Arch, Build-Conflicts, Build-Conflicts-Indep, Build-Conflicts-Arch) for details.