Bug 1352113 - Shippable Builds - Do not do linux32/opt build on integration. r=aki

Differential Revision: https://phabricator.services.mozilla.com/D23248

--HG--
extra : moz-landing-system : lando

taskcluster/ci/build/linux.yml

@@ -414,6 +414,7 @@ linux/opt:
         secrets: true
         tooltool-downloads: public
         need-xvfb: true
+    run-on-projects: ['mozilla-central', 'try']
     toolchains:
         - linux64-binutils
         - linux64-clang