Replace the native and ancient macOS assembler (/usr/bin/as) or the MacPorts assembler (/opt/local/bin/as) by a script which calls the clang assembler. Now removing "-I dir" options from the arguments passed to the assembler and taking into account possible spaces in ARG in the condition for the first if statement.

as

#!/bin/sh 
HAS_INPUT_FILE=0 
ARGS=$@ 
ARGS=$(echo $ARGS | perl -pe 's/-I.*?(\s-[^I])/\1/')
while [ $# -ne 0 ]; do 
        ARG=$1 
        # Skip options 
        if [ "$ARG" == "-arch" ] || [ "$ARG" == "-o" ]; then 
                # Skip next token 
                shift 
                shift 
                continue 
        fi 

        if [ `echo $ARG | head -c1` == "-" ]; then 
                shift 
                continue 
        fi 

        HAS_INPUT_FILE=1 
        break 
done 

if [ $HAS_INPUT_FILE -eq 1 ]; then 
        clang -c -x assembler $ARGS 
else 
        clang -c -x assembler $ARGS - 
fi