Upgrade to a newer version of toolchains_llvm

The old project has been renamed. This has caused tarball contents of
historical releases to change.

Fixes: #189

WORKSPACE

@@ -120,14 +120,14 @@ switched_rules_by_language(
 )
 
 http_archive(
-    name = "com_grail_bazel_toolchain",
-    canonical_id = "0.7.2",
-    sha256 = "f7aa8e59c9d3cafde6edb372d9bd25fb4ee7293ab20b916d867cd0baaa642529",
-    strip_prefix = "bazel-toolchain-0.7.2",
-    url = "https://github.com/grailbio/bazel-toolchain/archive/0.7.2.tar.gz",
+    name = "toolchains_llvm",
+    sha256 = "b7cd301ef7b0ece28d20d3e778697a5e3b81828393150bed04838c0c52963a01",
+    strip_prefix = "toolchains_llvm-0.10.3",
+    canonical_id = "0.10.3",
+    url = "https://github.com/grailbio/bazel-toolchain/releases/download/0.10.3/toolchains_llvm-0.10.3.tar.gz",
 )
 
-load("@com_grail_bazel_toolchain//toolchain:rules.bzl", "llvm_toolchain")
+load("@toolchains_llvm//toolchain:rules.bzl", "llvm_toolchain")
 
 llvm_toolchain(
     name = "llvm_toolchain",