Revert of Re-land "Fix double-building of v8 in GN builds"

snapshot_toolchain.gni

 # Copyright 2015 the V8 project authors. All rights reserved.
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are
 # met:
 #
 #     * Redistributions of source code must retain the above copyright
 #       notice, this list of conditions and the following disclaimer.
 #     * Redistributions in binary form must reproduce the above
 #       copyright notice, this list of conditions and the following
 #       disclaimer in the documentation and/or other materials provided
@@ skipping 20 matching lines @@
   # The snapshot needs to be compiled for the host, but compiled with
   # a toolchain that matches the bit-width of the target.
   v8_snapshot_toolchain = ""
 }
 
 # TODO(GYP): For now we only support 32-bit little-endian target builds from an
 # x64 Linux host. Eventually we need to support all of the host/target
 # configurations v8 runs on.
 if (v8_snapshot_toolchain == "") {
   if (host_cpu == "x64" && host_os == "linux") {
-    if (v8_current_cpu == v8_target_cpu && current_cpu == target_cpu &&
-        (target_cpu == "x86" || target_cpu == "x64")) {
-      # Args that are specified by the user can end up having the same
-      # effect as args that are specified in a toolchain; for example,
-      # building on linux x64 with target_cpu == "x86" v8_target_cpu == "arm"
-      # will use the //build/toolchain/linux:clang_x86 toolchain, but have the
-      # same effect as if you specified
-      #
-      #   custom_toolchain="//build/toolchain/linux:clang_x86_v8_arm"
-      #
-      # As a result, if we didn't take that into account we could
-      # accidentally end up building two identical copies of v8.
-      #
-      # So, we can re-use the default toolchain for the snapshot in these
-      # casees, but only when the host is actually capable of running the
-      # target code, which at this time means that the target_cpu == x86
-      # or x64.
-      v8_snapshot_toolchain = default_toolchain
+    if (current_cpu == "arm" || current_cpu == "mipsel" ||
+        current_cpu == "x86") {
+      _snapshot_cpu = "x86"
     } else {
-      if (current_cpu == "arm" || current_cpu == "mipsel" ||
-          current_cpu == "x86") {
-        _snapshot_cpu = "x86"
-      } else {
-        assert(current_cpu == "arm64" || current_cpu == "x64" ||
-                   current_cpu == "mips64el",
-               "Need environment for this arch: $current_cpu")
-        _snapshot_cpu = "x64"
-      }
+      assert(current_cpu == "arm64" || current_cpu == "x64" ||
+                 current_cpu == "mips64el",
+             "Need environment for this arch: $current_cpu")
+      _snapshot_cpu = "x64"
+    }
 
-      if (v8_current_cpu != _snapshot_cpu) {
-        _cpus = "${_snapshot_cpu}_v8_${v8_current_cpu}"
-      } else {
-        _cpus = _snapshot_cpu
-      }
+    if (v8_current_cpu != _snapshot_cpu) {
+      _cpus = "${_snapshot_cpu}_v8_${v8_current_cpu}"
+    } else {
+      _cpus = _snapshot_cpu
+    }
 
-      if ((host_os == "linux" && current_os == "android") || is_clang) {
-        v8_snapshot_toolchain = "//build/toolchain/linux:clang_${_cpus}"
-      } else {
-        v8_snapshot_toolchain = "//build/toolchain/linux:${_cpus}"
-      }
+    if ((host_os == "linux" && current_os == "android") || is_clang) {
+      v8_snapshot_toolchain = "//build/toolchain/linux:clang_${_cpus}"
+    } else {
+      v8_snapshot_toolchain = "//build/toolchain/linux:${_cpus}"
     }
   } else if (host_os == "mac" && current_os == "win") {
     assert(v8_current_cpu == current_cpu,
            "v8 target must match the regular target on this platform")
     v8_snapshot_toolchain = "//build/toolchain/mac:clang_$current_cpu"
   } else {
     v8_snapshot_toolchain = default_toolchain
   }
 }