fix(zkvmLib): Don't remove final entry in lockfile

The AWK script goes to the next line when a property is found. If the
lock file ends on a property, the next line will be "fetched", but that
is after the end of the file, so we'll never reach the printing logic.
We're adding a blank line to the end of the lock file, so we never hit
this edge case.

Author: Syndamia

zkvmLib.nix

@@ -78,6 +78,7 @@ let
 
         tail -n +4 ./guest/Cargo.lock >> lockfile
         tail -n +4 ../../guests/${guest}/Cargo.lock >> lockfile
+        echo >> lockfile
 
         awk '${removeDuplicates}' lockfile > "$out/Cargo.lock"
       '';