[GN] Add support for disabling opts via SK_BUILD_NO_OPTS define.

include/core/SkPreConfig.h

 /*
  * Copyright 2006 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 // IWYU pragma: private, include "SkTypes.h"
 
 #ifndef SkPreConfig_DEFINED
@@ skipping 100 matching lines @@
 
 #define SK_CPU_SSE_LEVEL_SSE1     10
 #define SK_CPU_SSE_LEVEL_SSE2     20
 #define SK_CPU_SSE_LEVEL_SSE3     30
 #define SK_CPU_SSE_LEVEL_SSSE3    31
 #define SK_CPU_SSE_LEVEL_SSE41    41
 #define SK_CPU_SSE_LEVEL_SSE42    42
 #define SK_CPU_SSE_LEVEL_AVX      51
 #define SK_CPU_SSE_LEVEL_AVX2     52
 
-#ifdef SK_BUILD_FOR_IOS
-    #define SK_CPU_SSE_LEVEL 0  // We're tired of fighting with opts/ and iOS simulator.
+// When targetting iOS and using gyp to generate the build files, it is not
+// possible to select files to build depending on the architecture (i.e. it
+// is not possible to use hand optimized assembly implementation). In that
+// configuration SK_BUILD_NO_OPTS is defined. Remove optimisation then.
+#ifdef SK_BUILD_NO_OPTS
+    #define SK_CPU_SSE_LEVEL 0
 #endif
 
 // Are we in GCC?
 #ifndef SK_CPU_SSE_LEVEL
     // 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
     #elif defined(__AVX__)
         #define SK_CPU_SSE_LEVEL    SK_CPU_SSE_LEVEL_AVX
@@ skipping 50 matching lines @@
                 || defined(__ARM_ARCH_5TEJ__) || defined(_ARM_ARCH_5)
             #define SK_ARM_ARCH 5
         #elif defined(__ARM_ARCH_4__) || defined(__ARM_ARCH_4T__) || defined(_ARM_ARCH_4)
             #define SK_ARM_ARCH 4
         #else
             #define SK_ARM_ARCH 3
         #endif
     #endif
 #endif
 
-// Disable ARM64 optimizations for iOS due to complications regarding gyp and iOS.
-#if defined(__aarch64__) && !defined(SK_BUILD_FOR_IOS)
+#if defined(__aarch64__) && !defined(SK_BUILD_NO_OPTS)
     #define SK_CPU_ARM64
 #endif
 
 // All 64-bit ARM chips have NEON.  Many 32-bit ARM chips do too.
-// TODO: Why don't we want NEON on iOS?
-#if !defined(SK_ARM_HAS_NEON) && !defined(SK_BUILD_FOR_IOS) && (defined(__ARM_NEON__) || defined(__ARM_NEON))
+#if !defined(SK_ARM_HAS_NEON) && !defined(SK_BUILD_NO_OPTS) && (defined(__ARM_NEON__) || defined(__ARM_NEON))
     #define SK_ARM_HAS_NEON
 #endif
 
 //////////////////////////////////////////////////////////////////////
 
 #if !defined(SKIA_IMPLEMENTATION)
     #define SKIA_IMPLEMENTATION 0
 #endif
 
 #if defined(SKIA_DLL)
@@ skipping 48 matching lines @@
  *
  * NOTE: Clang/ARM (r161757) does not support the 'optimize' attribute.
  */
 #if SK_HAS_ATTRIBUTE(optimize)
 #   define SK_ATTRIBUTE_OPTIMIZE_O1 __attribute__((optimize("O1")))
 #else
 #   define SK_ATTRIBUTE_OPTIMIZE_O1 /* nothing */
 #endif
 
 #endif