I was compiling Aspell in a folder named "~/Misc/ncurses 5.4 and
Aspell 0.60 stuff/aspell-0.60" and the compile died with the error
sed: stuff/aspell-0.60/libaspell.la: No such file or directory
libtool: link: `stuff/aspell-0.60/libaspell.la' is not a valid libtool
Once I changed the spaces in the folder name "ncurses 5.4 and
Aspell 0.60 stuff" to underscores, the compile worked. Looks like
some underquoting in a shell command.