add flag to rebaseline lowp bilerp_8888_clamp stage

See https://skia-review.googlesource.com/c/skia/+/121582

Bug: skia:7810
Change-Id: Ibc32853736c539e76d84e135e3ef45201056026b
Reviewed-on: https://chromium-review.googlesource.com/1014249Reviewed-by: Florin Malita <fmalita@chromium.org>
Commit-Queue: Mike Klein <mtklein@chromium.org>
Cr-Commit-Position: refs/heads/master@{#551123}

skia/config/SkUserConfig.h

@@ -224,6 +224,7 @@ SK_API void SkDebugf_FileLine(const char* file, int line, bool fatal,
 // Max. verb count for paths rendered by the edge-AA tessellating path renderer.
 #define GR_AA_TESSELLATOR_MAX_VERB_COUNT 10
 
+#define SK_DISABLE_LOWP_BILERP_CLAMP_CLAMP_STAGE
 
 #ifndef SK_SUPPORT_LEGACY_PATH_DAA_BIT
 #define SK_SUPPORT_LEGACY_PATH_DAA_BIT