Revert of 'Adding target to build SwiftShader'

BUILD.gn

Index: BUILD.gn
diff --git a/BUILD.gn b/BUILD.gn
index 5410341241ed8cc5e5473e8ea72eed87a06dc8f2..e2f1bbd61887f7926e5ec355c4ed05006e06f3ff 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -501,11 +501,6 @@ group("both_gn_and_gyp") {
     ]
   }
 
-  # TODO(sugoi) bug 644737: Remove the '!is_clang' condition once __nop is supported by clang-cl
-  if (is_linux || (is_win && !is_clang)) {
-    deps += [ "//third_party/swiftshader" ]
-  }
-
   # TODO(GYP): Figure out which of these should (and can) build
   # for chromeos/ios.
   if (!is_chromeos && !is_ios) {