Update bazel-toolchains (#173)

diff --git a/WORKSPACE b/WORKSPACE
index 40e9b55..ac6d1b6 100644
--- a/WORKSPACE
+++ b/WORKSPACE
@@ -31,11 +31,11 @@
 
 http_archive(
     name = "bazel_toolchains",
-    sha256 = "7e85a14821536bc24e04610d309002056f278113c6cc82f1059a609361812431",
-    strip_prefix = "bazel-toolchains-bc0091adceaf4642192a8dcfc46e3ae3e4560ea7",
+    sha256 = "109a99384f9d08f9e75136d218ebaebc68cc810c56897aea2224c57932052d30",
+    strip_prefix = "bazel-toolchains-94d31935a2c94fe7e7c7379a0f3393e181928ff7",
     urls = [
-        "https://mirror.bazel.build/github.com/bazelbuild/bazel-toolchains/archive/bc0091adceaf4642192a8dcfc46e3ae3e4560ea7.tar.gz",
-        "https://github.com/bazelbuild/bazel-toolchains/archive/bc0091adceaf4642192a8dcfc46e3ae3e4560ea7.tar.gz",
+        "https://mirror.bazel.build/github.com/bazelbuild/bazel-toolchains/archive/94d31935a2c94fe7e7c7379a0f3393e181928ff7.tar.gz",
+        "https://github.com/bazelbuild/bazel-toolchains/archive/94d31935a2c94fe7e7c7379a0f3393e181928ff7.tar.gz",
     ],
 )