Makefile.mk: Use one line per *_common flag

Use one line per *_common flag like it's done elsewhere in the tree.
It makes the list of options more readable.

Change-Id: I33c500e6eb74daf1e66c2b5e07b50f81c0f4587d
Signed-off-by: Felix Singer <felixsinger@posteo.net>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/83226
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Elyes Haouas <ehaouas@noos.fr>
Reviewed-by: Maximilian Brune <maximilian.brune@9elements.com>

0 files changed, 0 insertions, 0 deletions