Hi Maxim! I think I solved this already last year without the need for FHS by building GCC with hard coded paths for all standard C/C++ files.
Please search for “a different way to build GCC” in the guix-devel mailing list or take a look at <[1] https://git.pub.solar/stefan/embedded-channel>, especially into the file embedded.scm. It builds a native GCC first (with all that troubles solved), which is then used to build embedded cross GCCs. Bye Stefan References 1. https://git.pub.solar/stefan/embedded-channel
