Make SkShaper's GN setup more DLL friendly

Similar to the Skottie refactor that just landed, this avoids having an
empty component when shaper is disabled (which turns into a DLL with no
sources, and a missing DllMain). I think this pattern of having modules
expose the same components as empty groups is simpler (and also fixes
the fact that only two of N references in top-level BUILD.gn were
guarded). Also, no one is using the define?

Change-Id: I9d25c1cfbd42336874f4428bf61f3e34a4a18d3c
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/207303
Reviewed-by: Mike Klein <mtklein@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
3 files changed