[bazel] Move codec flags to source folder

Bug: skia:12541
Change-Id: I50bae13f0bb054de35e84a3df8df4aa9fdc8952a
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/566877
Reviewed-by: Joe Gregorio <jcgregorio@google.com>
8 files changed