Fix bazel build on Mac M1 (aarch64)

Running the bazel build on Mac M1 yields the following error:

Configurable attribute "actual" doesn't match this configuration:
Could not find a JDK for host execution environment, please explicitly
provide one using `--host_javabase.`

Follow hints in [1] and fix this by loading bazel platforms 0.0.5
which contains a fix [2] making aarch64 an alias of arm64.

[1] bazelbuild/bazel#13573
[2] bazelbuild/platforms#22

Release-Notes: Fix bazel build on Mac M1 (aarch64)
Change-Id: I5a4ebcd50012a53e5ff92a12e4fa8ba766aed0a7

WORKSPACE

@@ -32,6 +32,15 @@ load("//tools/bzl:maven_jar.bzl", "GERRIT", "MAVEN_LOCAL", "maven_jar")
 load("//plugins:external_plugin_deps.bzl", "external_plugin_deps")
 load("//tools:nongoogle.bzl", "declare_nongoogle_deps")
 
+http_archive(
+    name = "platforms",
+    sha256 = "379113459b0feaf6bfbb584a91874c065078aa673222846ac765f86661c27407",
+    urls = [
+        "https://mirror.bazel.build/github.com/bazelbuild/platforms/releases/download/0.0.5/platforms-0.0.5.tar.gz",
+        "https://github.com/bazelbuild/platforms/releases/download/0.0.5/platforms-0.0.5.tar.gz",
+    ],
+)
+
 http_archive(
     name = "rbe_jdk11",
     sha256 = "766796de71916118e528b9f4334c29c9c9b4e926227bf3264dee555e6a4306c8",