Revert "SKIA_IMPLEMENTATION is only relevant in shared builds"

This reverts commit 8413ff13fefa1e88cd3fc67ebaed87c9eb3419c7.

Reason for revert: turns out that's not true.  It's how we pick the right Vulkan headers.

Original change's description:
> SKIA_IMPLEMENTATION is only relevant in shared builds
> 
> Change-Id: If4ce780a74d59e5ec5c9d950a560527d4de7e030
> Reviewed-on: https://skia-review.googlesource.com/c/skia/+/210130
> Commit-Queue: Brian Osman <brianosman@google.com>
> Auto-Submit: Mike Klein <mtklein@google.com>
> Reviewed-by: Brian Osman <brianosman@google.com>

TBR=mtklein@google.com,halcanary@google.com,brianosman@google.com

# Not skipping CQ checks because original CL landed > 1 day ago.

Change-Id: I35fc5458930254597279875125bb392af4b8e74c
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/211092
Commit-Queue: Mike Klein <mtklein@google.com>
Reviewed-by: Mike Klein <mtklein@google.com>
diff --git a/BUILD.gn b/BUILD.gn
index 840f0a5..b1bfd94 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -164,9 +164,7 @@
 # Any code that's linked into Skia-the-library should use this config via += skia_library_configs.
 config("skia_library") {
   visibility = [ ":*" ]
-  if (is_component_build) {
-    defines = [ "SKIA_IMPLEMENTATION=1" ]
-  }
+  defines = [ "SKIA_IMPLEMENTATION=1" ]
 }
 
 skia_library_configs = [