Fix keccak build for Windows

third_party/ethash/BUILD.gn

@@ -1,19 +1,10 @@
-source_set("ethash") {
+static_library("ethash") {
   configs -= [ "//build/config/compiler:chromium_code" ]
   configs += [ "//build/config/compiler:no_chromium_code" ]
   include_dirs = [ "src/include" ]
   sources = [
-    "src/lib/ethash/bit_manipulation.h",
-    "src/lib/ethash/builtins.h",
-    "src/lib/ethash/endianness.hpp",
-    "src/lib/ethash/ethash-internal.hpp",
-    "src/lib/ethash/ethash.cpp",
-    "src/lib/ethash/kiss99.hpp",
-    "src/lib/ethash/managed.cpp",
-    "src/lib/ethash/primes.c",
-    "src/lib/ethash/primes.h",
-    "src/lib/ethash/progpow.cpp",
-    "src/lib/keccak/keccak.c",
-    "src/lib/support/attributes.h",
+    "keccak_override.c",
+    "src/include/ethash/hash_types.h",
+    "src/include/ethash/keccak.h",
   ]
 }

third_party/ethash/keccak_override.c

@@ -0,0 +1,10 @@
+#include "build/build_config.h"
+
+// The use of __builtin_cpu_init is wrapped around an __X86_64__ ifdef.
+// Since this isn't available in vc++ and since it's only needd on macOS,
+// we exclude this block with the following hack.
+#if defined(OS_WIN)
+#undef __x86_64__
+#endif
+
+#include "src/lib/keccak/keccak.c"