Disable AVX2 code to prevent build failure with GCC

Bug: https://bugs.gentoo.org/608640

--- a/third_party/skia/include/core/SkPreConfig.h
+++ b/third_party/skia/include/core/SkPreConfig.h
@@ -125,7 +125,7 @@
     // These checks must be done in descending order to ensure we set the highest
     // available SSE level.
     #if defined(__AVX2__)
-        #define SK_CPU_SSE_LEVEL    SK_CPU_SSE_LEVEL_AVX2
+        #define SK_CPU_SSE_LEVEL    SK_CPU_SSE_LEVEL_AVX
     #elif defined(__AVX__)
         #define SK_CPU_SSE_LEVEL    SK_CPU_SSE_LEVEL_AVX
     #elif defined(__SSE4_2__)