proper lines (amending 59b6f0462086);

--- a/src/Tools/Setup/isabelle/setup/Library.java	Wed Jul 14 11:37:35 2021 +0200
+++ b/src/Tools/Setup/isabelle/setup/Library.java	Thu Jul 15 12:51:11 2021 +0200
@@ -37,6 +37,7 @@
             for (String s : split_lines(str)) {
                 result.append(prfx);
                 result.append(s);
+                result.append('\n');
             }
             return result.toString();
         }