Hi @ashraz ! Thanks for you quick response!
The contents of the manifest.scm right now are quite straightforward:
(use-modules (guix packages)
(gnu packages base))
(specifications->manifest
(list "clang-toolchain"
"coreutils"
"file"
"gcc-toolchain"
"git"
"glibc"
"nss-certs"
"python"
"python-pip"))
Once inside the guix container I run pip install platformio to have the pio utility available.
To discard the gcc misconfiguration I used the docker python image to run pio run -v and compared with the guix container one as you suggested. Both use the xtensa-esp32-elf-gcc as expected. The python one finished successfully, since I guess Ubuntu’s glibc package includes 32-bit headers… which brings me back to the fight of being able to have glibc with 32-bit headers available on the guix container… unless someone has a better idea.