Make generated effects from sksl fp files not need SK_SUPPORT_GPU

Bug: skia:
Change-Id: I42a5c7fe7dc35a23290c8daa754c9fcce07f76fb
Reviewed-on: https://skia-review.googlesource.com/119010
Commit-Queue: Greg Daniel <egdaniel@google.com>
Reviewed-by: Robert Phillips <robertphillips@google.com>
diff --git a/gn/gpu.gni b/gn/gpu.gni
index b3f4eb1..c9fd2f3 100644
--- a/gn/gpu.gni
+++ b/gn/gpu.gni
@@ -319,6 +319,8 @@
 
   "$_src/gpu/effects/GrAARectEffect.cpp",
   "$_src/gpu/effects/GrAARectEffect.h",
+  "$_src/gpu/effects/GrAlphaThresholdFragmentProcessor.cpp",
+  "$_src/gpu/effects/GrAlphaThresholdFragmentProcessor.h",
   "$_src/gpu/effects/GrArithmeticFP.cpp",
   "$_src/gpu/effects/GrArithmeticFP.h",
   "$_src/gpu/effects/GrBlurredEdgeFragmentProcessor.cpp",