Gdb fails to build with Python 3.7

[byllgrim]

Hi.

Building pulp-platform/pulp-riscv-gnu-toolchain errors out when I compile on arch linux.
It seems you have the same problem as riscv/riscv-binutils-gdb has:
riscvarchive/riscv-binutils-gdb#161

"With Python 3.7, gdb fails to build because it uses internal-only function _PyImport_FixupBuiltin whose signature has changed."

Regards Robin.