When copying over the binaries, use '-p' to preserve date/time

When copying over the binaries, use '-p' to preserve date/time

Although I can't reproduce it, others are seeing different lex/yacc
programs always regenerated after my change to copy rather than
symlink the files. The reported fix is to add '-p' to the copies.
Since it doesn't hurt, go head and add it, though the reasons for
this mattering remain at best obscure and poorly articulated.