pt-build can't properly configure the build environment for building firefox: it can't find the proper dependencies in the system.

[Gregório Assagra de Almeida Filho]

under ubuntu 20.04, apt-build doesn't seems to be prepared to deal with modern .deb packages.
Most of the time it fails to build source packages, and this doesn't seems to affect as much other projects like apt-src.

ProblemType: Bug
DistroRelease: Ubuntu 20.04
Package: apt-build 0.12.47
ProcVersionSignature: Ubuntu 5.8.0-53.60~20.04.1-generic 5.8.18
Uname: Linux 5.8.0-53-generic x86_64
ApportVersion: 2.20.11-0ubuntu27.17
Architecture: amd64
CasperMD5CheckResult: skip
Date: Sat May 22 15:50:25 2021
DistributionChannelDescriptor:
 # This is the distribution channel descriptor for the OEM CDs
 # For more information see http://wiki.ubuntu.com/DistributionChannelDescriptor
 canonical-oem-somerville-focal-amd64-20200502-85
InstallationDate: Installed on 2021-05-13 (8 days ago)
InstallationMedia: Ubuntu 20.04 "Focal" - Build amd64 LIVE Binary 20200502-05:58
ProcEnviron:
 LANGUAGE=pt_BR:pt:en
 LANG=pt_BR.UTF-8
 TERM=xterm-256color
 PATH=(custom, no user)
 SHELL=/bin/bash
SourcePackage: apt-build
UpgradeStatus: No upgrade log present (probably fresh install)
mtime.conffile..etc.apport.crashdb.conf: 2021-05-22T15:28:41.256238