Preface This method of compiling for armel (e.g. ARMv5, earlier, and some ARMv6) which uses pbuilder in an ARM HardFloat VM is not recommended as it is extremely slow (because of running in a emulated VM, not because of using pbuilder).
Preface Unless you have a new, high-powered, ARM system with which to build, the fastest and most practical way to build software for armel (early ARM CPU versions) is to cross-compile on an x86_64 machine (Debian and offshoots call this the amd64 architecture, even for non-AMD CPUs).
Overview The cross-compilation toolchains builtin to most modern Linux distributions do not support older versions of GCC. For old kernels (and other software) that require GCC4 or lower for building, this poses a challenge.