build system: provide generic compiler flag variables

Introduce generic-$(type)-ccopts and $(class)-generic-ccopts
to declare compiler flags that apply to all files of a certain
type or of a certain class. Then use them.

This is inspired by the commit listed below, but rewritten to match
upstream, and split in smaller pieces to keep intent clear.

Change-Id: I655688e82a0cc5bad89b6f55dc217b9f66b64604
Signed-off-by: Patrick Georgi <pgeorgi@chromium.org>
Based-On-Change-Id: I50af7dacf616e0f8ff4c43f4acc679089ad7022b
Based-On-Signed-off-by: Julius Werner <jwerner@chromium.org>
Based-On-Reviewed-on: https://chromium-review.googlesource.com/219170
Reviewed-on: http://review.coreboot.org/9114
Tested-by: build bot (Jenkins)
Reviewed-by: Aaron Durbin <adurbin@google.com>
4 files changed