reverted bazel-toolchains alias to its original form

third_party/toolchains/BUILD

@@ -35,8 +35,8 @@ platform(
         "@bazel_tools//platforms:x86_64",
         "@bazel_tools//platforms:linux",
         "@bazel_tools//tools/cpp:clang",
-        "@bazel_toolchains//constraints:xenial",
-        "@bazel_toolchains//constraints/sanitizers:support_msan",
+        "@com_github_bazelbuild_bazeltoolchains//constraints:xenial",
+        "@com_github_bazelbuild_bazeltoolchains//constraints/sanitizers:support_msan",
         "//third_party/toolchains/machine_size:standard",
     ],
     remote_execution_properties = """
@@ -58,8 +58,8 @@ platform(
         "@bazel_tools//platforms:x86_64",
         "@bazel_tools//platforms:linux",
         "@bazel_tools//tools/cpp:clang",
-        "@bazel_toolchains//constraints:xenial",
-        "@bazel_toolchains//constraints/sanitizers:support_msan",
+        "@com_github_bazelbuild_bazeltoolchains//constraints:xenial",
+        "@com_github_bazelbuild_bazeltoolchains//constraints/sanitizers:support_msan",
         "//third_party/toolchains/machine_size:large",
     ],
     remote_execution_properties = """
@@ -82,8 +82,8 @@ toolchain(
         "@bazel_tools//platforms:linux",
         "@bazel_tools//platforms:x86_64",
         "@bazel_tools//tools/cpp:clang",
-        "@bazel_toolchains//constraints:xenial",
-        "@bazel_toolchains//constraints/sanitizers:support_msan",
+        "@com_github_bazelbuild_bazeltoolchains//constraints:xenial",
+        "@com_github_bazelbuild_bazeltoolchains//constraints/sanitizers:support_msan",
         "//third_party/toolchains/machine_size:standard",
         "//third_party/toolchains/machine_size:large",
     ],
@@ -93,6 +93,6 @@ toolchain(
         "@bazel_tools//platforms:linux",
         "@bazel_tools//platforms:x86_64",
     ],
-    toolchain = "@bazel_toolchains//configs/ubuntu16_04_clang/1.1/bazel_0.16.1/default:cc-compiler-k8",
+    toolchain = "@com_github_bazelbuild_bazeltoolchains//configs/ubuntu16_04_clang/1.1/bazel_0.16.1/default:cc-compiler-k8",
     toolchain_type = "@bazel_tools//tools/cpp:toolchain_type",
 )