build: Use newline at the end of echo to apkcerts file

Revert "core/Makefile: avoid exceeding MAX_ARG_STRLEN"
This reverts commit 2eb4ca0f.

If a newline is not used, the echo commands are strung
together in one large command. In environments with long
pathnames, this can cause the error:
  "make: execvp: /bin/bash: Argument list too long"

This splits the echo commands up into individual commands
to avoid the argument limit.

Change-Id: Id2e5033ad51a9746e2b6cd88f9d53d5b7c93bc1b