I would have expected that CXXFLAGS="-mno-sse4.1" ./configure
would make the sse4.1 intrinsics check fail but it doesn’t:
0configure:23377: checking for SSE4.1 intrinsics
1configure:23396: clang++ -std=c++17 -c -msse4.1 -mno-sse4.1 conftest.cpp >&5
2configure:23396: $? = 0
3configure:23398: result: yes
Not sure what is going on here, seems like a bug.