Even more DLL build fixes

These changes let us build a non-official component build on Windows,
using either MSVC or clang

Change-Id: Ia3279aa19e007e70ff28925ff70a0bfe8144d96f
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/207307
Reviewed-by: Mike Klein <mtklein@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>