manibuilder/anita: Move environment overrides to Makefile.anita

Also be specific where we have to allow warnings and drop a long unused
override for anita:7.1-sparc.

Change-Id: I962ecbbeee2813237421ab866b54f2de79cc4a20
Signed-off-by: Nico Huber <nico.h@gmx.de>
Reviewed-on: https://review.coreboot.org/c/flashrom-stable/+/73773
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
2 files changed