doc: update list of archs supporting -race

Change-Id: Id0a55674a16671aaee99182d9096a9263f7a80b3
Reviewed-on: https://go-review.googlesource.com/c/go/+/189357Reviewed-by: Ian Lance Taylor <iant@golang.org>

doc/articles/race_detector.html

@@ -377,8 +377,11 @@ func (w *Watchdog) Start() {
 <h2 id="Supported_Systems">Supported Systems</h2>
 
 <p>
-The race detector runs on <code>darwin/amd64</code>, <code>freebsd/amd64</code>,
-<code>linux/amd64</code>, and <code>windows/amd64</code>.
+  The race detector runs on
+  <code>linux/amd64</code>, <code>linux/ppc64le</code>,
+  <code>linux/arm64</code>, <code>freebsd/amd64</code>,
+  <code>netbsd/amd64</code>, <code>darwin/amd64</code>,
+  and <code>windows/amd64</code>.
 </p>
 
 <h2 id="Runtime_Overheads">Runtime Overhead</h2>