There may be many reasons why you must have filesystem that is case sensitive.  For example, you are trying to run ct-ng build command and it fails under Windows WSL.

Solution is to mount your filesystem with case sensitive enabled, or use per-directory control.  The second option gives your more control, but the sub-directories do not inherit properties from the parent.  To do that, open a command shell as an administrator and run:

fsutil file setCaseSensitiveInfo <directory> enable

First option, to mount your directory under WSL as case-sensitive file system, edit (create if it doesn't exist) /etc/wsl.conf and add:

options = "case=force"

Restart WSL shell so that the configuration can be read.  Type mount command and you should see:

C: on /mnt/c type drvfs (rw,noatime,uid=1000,gid=1000,case=force)

Notice case=force option listed in the parenthesis.  Now ct-ng build command will not complain.