Updating bazelbuild/platforms

WARNING: These are what worked last time. Reality might be different.

Step 1: Make the release

• Pick a new version number

• Run distro/makerel.sh version

• Go to the Releases page

• Draft a new release

  • Name the release with a version number
  • Use the version number as the title
  • Copy the description that makerel.sh produced to the description field.
  • upload the generated tar file

• use https://github.com/bazelbuild/continuous-integration/blob/master/mirror/mirror.sh to mirror the file

Step 2: Update Bazel

• Edit distdir_deps.bzl
• Merge the PR

Sample diff:

diff --git a/distdir_deps.bzl b/distdir_deps.bzl
index ed49a563bc..1739a25c2a 100644
--- a/distdir_deps.bzl
+++ b/distdir_deps.bzl
@@ -20,11 +20,11 @@ DIST_DEPS = {
     #
     ########################################
     "platforms": {
-        "archive": "platforms-0.0.2.tar.gz",
-        "sha256": "48a2d8d343863989c232843e01afc8a986eb8738766bfd8611420a7db8f6f0c3",
+        "archive": "platforms-0.0.3.tar.gz",
+        "sha256": "460caee0fa583b908c622913334ec3c1b842572b9c23cf0d3da0c2543a1a157d",
         "urls": [
-            "https://mirror.bazel.build/github.com/bazelbuild/platforms/releases/download/0.0.2/platforms-0.0.2.tar.gz",
-            "https://github.com/bazelbuild/platforms/releases/download/0.0.2/platforms-0.0.2.tar.gz",
+            "https://mirror.bazel.build/github.com/bazelbuild/platforms/releases/download/0.0.3/platforms-0.0.3.tar.gz",
+            "https://github.com/bazelbuild/platforms/releases/download/0.0.3/platforms-0.0.3.tar.gz",
         ],
         "used_in": [
             "additional_distfiles",