Add build and release instructions

Author: grendello

README.md

@@ -15,3 +15,24 @@ The Binutils sources are built in this repository without any changes.
 After the build is done, we create a tarball with the binaries for
 Linux, macOS and Windows.  The tarball is then used by Xamarin.Android
 to package the utilities for Xamarin.Android distribution.
+
+# How to build and publish new version of GNU Binutils
+
+  1. Edit `.github/workflows/ci.yml`
+  2. Set the `BINUTILS_VERSION` variable to the new version number of
+     the upstream package.
+  3. Commit and push the changes
+  4. After the build finishes, visit the Actions tab, find the run
+     corresponding to commit from `3.` above, download the
+     `Xamarin.Android` artifact
+  5. On your local machine, execute the release preparation script:
+     ```shell
+  ./prepare-release.sh PATH_TO_ARTIFACT_FROM_4 TAG_NAME
+     ```
+     `TAG_NAME` should be created by concatenating the Binutils version
+     with the `-XA.NUM` string, where `NUM` is an integer increasing
+     monotonously each time a new release of the same Binutils version
+     is made.
+  6. The script will produce a `7-zip` package on your local disk and
+     display instructions how to proceed with the release.
+	 

prepare-release.sh

@@ -60,7 +60,7 @@ function prepare()
 	cat <<EOF
 Next steps:
 
-  * Go to https://github.com/grendello/xamarin-android-binutils/releases
+  * Go to https://github.com/xamarin/xamarin-android-binutils/releases
   * Create new release using the ${TAG_NAME} tag
   * Upload ${dest_archive} to that release
 EOF