migrating to usage of rbe_preconfig and remove bazel-toolchains (#134)

* update bazel-toolchain 5.1.2

* remove deprecated rbe_autoconfig

* use rbe_preconfig and remove usage of bazel-toolchains as it was only included for the deprecated rbe_autoconfig

* change name to buildkite_config

* reformat WORKSPACE

WORKSPACE

@@ -21,15 +21,15 @@ http_archive(
 )
 
 http_archive(
-    name = "bazel_toolchains",
-    sha256 = "1caf8584434d3e31be674067996be787cfa511fda2a0f05811131b588886477f",
-    strip_prefix = "bazel-toolchains-3.7.2",
-    urls = [
-        "https://github.com/bazelbuild/bazel-toolchains/releases/download/3.7.2/bazel-toolchains-3.7.2.tar.gz",
-        "https://mirror.bazel.build/github.com/bazelbuild/bazel-toolchains/archive/3.7.2.tar.gz",
-    ],
+    name = "bazelci_rules",
+    sha256 = "eca21884e6f66a88c358e580fd67a6b148d30ab57b1680f62a96c00f9bc6a07e",
+    strip_prefix = "bazelci_rules-1.0.0",
+    url = "https://github.com/bazelbuild/continuous-integration/releases/download/rules-1.0.0/bazelci_rules-1.0.0.tar.gz",
 )
 
-load("@bazel_toolchains//rules:rbe_repo.bzl", "rbe_autoconfig")
+load("@bazelci_rules//:rbe_repo.bzl", "rbe_preconfig")
 
-rbe_autoconfig(name = "buildkite_config")
+rbe_preconfig(
+    name = "buildkite_config",
+    toolchain = "ubuntu1804-bazel-java11",
+)