gcc -print-search-dirs

gcc -print-search-dirs | while read -r line; do
   x="${line%%:*}"
   dirs="${line#*:}"
   echo $x;
   for dir in $(echo $dirs | sed 's/:/\n/g'); do
      echo "  $(realpath $dir 2>/dev/null)"
   done |
   sort -u
done

install
  /usr/lib/gcc/x86_64-linux-gnu/10
programs

  /usr/lib/gcc/x86_64-linux-gnu
  /usr/lib/gcc/x86_64-linux-gnu/10
libraries

  /lib
  /lib/x86_64-linux-gnu
  /lib/x86_64-linux-gnu/10
  /usr/lib
  /usr/lib/x86_64-linux-gnu
  /usr/lib/x86_64-linux-gnu/10