clarify about spaces in filenames on Windows
When building using msys2, the user directory inside home absolutely cannot have spaces inside it.
Add a line to explain this in the build instructions. Tell the user to see the name of the account they're currently logged in with, and then check the directory name for that account in C:\Users. If the account has a space in it (like "My User" or "Home Computer", you cannot continue. You must create a new user account with no spaces in it, log in as that user, and start all over. (There are probably easier workarounds if you want to wing it, but we won't answer bug reports if you take that route.)