Add bazel-toolchains to //:srcs

Signed-off-by: Philipp Wollermann <philwo@google.com>

third_party/BUILD

diff --git a/third_party/BUILD b/third_party/BUILD
index 53fa274..8819c69 100644
--- a/third_party/BUILD
+++ b/third_party/BUILD
@@ -10,6 +10,7 @@
         "//third_party/animal_sniffer:srcs",
         "//third_party/antlr:srcs",
         "//third_party/aws-sdk-auth-lite:srcs",
+        "//third_party/bazel-toolchains:srcs",
         "//third_party/checker_framework_dataflow:srcs",
         "//third_party/checker_framework_javacutil:srcs",
         "//third_party/css/bootstrap:srcs",

third_party/bazel-toolchains/BUILD

diff --git a/third_party/bazel-toolchains/BUILD b/third_party/bazel-toolchains/BUILD
index e69de29..4090932 100644
--- a/third_party/bazel-toolchains/BUILD
+++ b/third_party/bazel-toolchains/BUILD
@@ -0,0 +1,9 @@
+licenses(["notice"])  #  Apache-2 license
+
+filegroup(
+    name = "srcs",
+    srcs = glob(["**/*"]),
+    visibility = ["//third_party:__pkg__"],
+)
+
+exports_files(["bazel-toolchains-4.0.0-fix-version-check.patch"])