bazel: create rules for precompile srcs/hdrs.

Create two Bazel rules to publish the precompile source and header files.
These are currently unreferenced by other Bazel rules, but are needed to
generate the skia_precompile_sources and skia_precompile_public file
lists in //gn/core.gni, which currently exposes them.

Bug: skia:13485
Change-Id: I9eef76fef0490a70a36d93e664432d9ee80333bb
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/567477
Reviewed-by: Kevin Lubick <kjlubick@google.com>
2 files changed