Cannot "cd" or change directory using bash script in WSL [duplicate]
It's because you have created your script in a windows machine, some \r (carriage return) has been added at the end of each line.
Remove them like this:
tr -d '\r' < test.sh > new-test.sh
Also quote the variable's value:
cd "$dir"
then run your script:
./new-test.sh
As a hint it's also better to use:
cd ... || exit
in case of any failure.
Configure your editor so it uses Linux format for saving files (If it's capable of) or use an editor in bash like nano:
Another option is to using dos2unix command to convert the file to Unix type format.
Usage:
dos2unix your_file