Guard SIMD code with !defined(SKNX_NO_SIMD).

src/core/Sk4x.h

Index: src/core/Sk4x.h
diff --git a/src/core/Sk4x.h b/src/core/Sk4x.h
index d280c1b3783a03a1217c09bf63c78ec8967345cc..cbf4a1daee12ac882433db35bdd1e2dcaac4b122 100644
--- a/src/core/Sk4x.h
+++ b/src/core/Sk4x.h
@@ -2,11 +2,12 @@
 #define Sk4x_DEFINED
 
 #include "SkTypes.h"
+#include "SkNx.h"
 
 #define SK4X_PREAMBLE 1
-    #if SK_CPU_SSE_LEVEL >= SK_CPU_SSE_LEVEL_SSE2
+    #if SK_CPU_SSE_LEVEL >= SK_CPU_SSE_LEVEL_SSE2 && !defined(SKNX_NO_SIMD)
         #include "../opts/Sk4x_sse.h"
-    #elif defined(SK_ARM_HAS_NEON)
+    #elif defined(SK_ARM_HAS_NEON)                && !defined(SKNX_NO_SIMD)
         #include "../opts/Sk4x_neon.h"
     #else
         #include "../opts/Sk4x_none.h"
@@ -81,9 +82,9 @@ private:
     template <typename S> friend class Sk4x;
 
 #define SK4X_PRIVATE 1
-    #if SK_CPU_SSE_LEVEL >= SK_CPU_SSE_LEVEL_SSE2
+    #if SK_CPU_SSE_LEVEL >= SK_CPU_SSE_LEVEL_SSE2 && !defined(SKNX_NO_SIMD)
         #include "../opts/Sk4x_sse.h"
-    #elif defined(SK_ARM_HAS_NEON)
+    #elif defined(SK_ARM_HAS_NEON)                && !defined(SKNX_NO_SIMD)
         #include "../opts/Sk4x_neon.h"
     #else
         #include "../opts/Sk4x_none.h"
@@ -91,9 +92,9 @@ private:
 #undef SK4X_PRIVATE
 };
 
-#if SK_CPU_SSE_LEVEL >= SK_CPU_SSE_LEVEL_SSE2
+#if SK_CPU_SSE_LEVEL >= SK_CPU_SSE_LEVEL_SSE2 && !defined(SKNX_NO_SIMD)
     #include "../opts/Sk4x_sse.h"
-#elif defined(SK_ARM_HAS_NEON)
+#elif defined(SK_ARM_HAS_NEON)                && !defined(SKNX_NO_SIMD)
     #include "../opts/Sk4x_neon.h"
 #else
     #include "../opts/Sk4x_none.h"