build: remove duplicate const declaration

clang complains about this. I don't remember why I did this.
lib: don't use strlcpy() when strcpy() just works

clang complains when we use strlcpy() with strlen() on the source. The
change was made because some other tools complained that we used
strcpy() instead of a more secure version. Since they don't agree, let's
switch to the saner thing to do: use strcpy() when it is safe to do.