Add myself to build/OWNERS

R=cjhopman@chromium.org,scottmg@chromium.org,thakis@chromium.org
NOTRY=true

Review URL: https://codereview.chromium.org/842133003

Cr-Original-Commit-Position: refs/heads/master@{#310793}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: be3f4399b1e6272970a5a061c76d7993a629dcb9

OWNERS

@@ -1,3 +1,4 @@
 cjhopman@chromium.org
+jochen@chromium.org
 scottmg@chromium.org
 thakis@chromium.org