Makefile: build with -pipe

This saves the lifetime of my laptop's SSD by not creating as many temporary files, thus causing much fewer read/write operations.

Change-Id: I962e32ad40421ba564840de39748242d50acd84a
Signed-off-by: zwliew <zhaoweiliew@gmail.com>
Makefile: add -mcpu flag for good measure

Just in case for whatever reason GCC doesn't understand -mtune and -march lol

Change-Id: I783feae9e234dc564445d5c39be78757efdadf00
Signed-off-by: zwliew <zhaoweiliew@gmail.com>