Delete all files without extention and *.o

#!/bin/bash
PWD=$(pwd)
echo "C remove. Delete all files without extention and *.o"
echo "Work dir: [$PWD]"
if (whiptail --title  "Answer please Yes/No" --yesno  "Do you realy wan't delete all files without extention in $PWD" 10 60)  then
    ##echo "You chose Yes. Exit status was $?."
    echo "Delete files without extention";
    files=$(ls | grep -v '\.')
    for entry in $files
    do
        if [ $entry = "Makefile" ]; then
            echo "No delete Makefile"
        else
            echo "Delete file "$entry
            rm -f $entry
        fi
    done
    echo "Delete files with .o extention";
    rm -f *.o
else
     echo "Exit whithout action. Exit status=$?"