E build-depends-on-build-essential

You depend on the build-essential package, which is only a metapackage depending on build tools that have to be installed in all build environments.

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.