py-cython tries using Xcode clang on Rosetta (for ppc), needs to be blacklisted

[barracuda156]

/usr/bin/clang -fno-common -dynamic -DNDEBUG -g -fwrapv -O3 -Wall -pipe -Os -arch ppc -isysroot/ -I/opt/local/Library/Frameworks/Python.framework/Versions/3.11/include/python3.11 -c /opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_macports_release_tarballs_ports_python_py-cython/py311-cython/work/Cython-0.29.32/Cython/Compiler/Scanning.c -o build/temp.macosx-10.6-ppc-cpython-311/opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_macports_release_tarballs_ports_python_py-cython/py311-cython/work/Cython-0.29.32/Cython/Compiler/Scanning.o
clang: warning: not using the clang compiler for the 'powerpc' architecture

Either {clang < 421} should be added to blacklist or, if it works fine on x86, Xcode clang is to be blacklisted for PPC.