Cython directive 'language_level' not set, using 2 for now (Py2)

[mithro]

https://github.com/SymbiFlow/fasm/runs/3877602211?check_suite_focus=true#step:7:34

/opt/hostedtoolcache/Python/3.7.12/x64/lib/python3.7/site-packages/Cython/Compiler/Main.py:369: FutureWarning: Cython directive 'language_level' not set, using 2 for now (Py2). This will change in a later release! File: /home/runner/work/fasm/fasm/fasm/parser/antlr_to_tuple.pyx