Fix release process

The documented release process is to do npm run recompile, merge the
resulting branch to develop, and then do npm run relase, which does
not do another build.

This process should probably be changed, but for the moment ensure
that npm run recompile (as well as npm run package:beta) runs
buildTasks.checkinBuilt after each .build to preserve the old procedure.

scripts/gulpfiles/git_tasks.js

@@ -103,7 +103,9 @@ const updateGithubPages = gulp.series(
     execSync('git reset --hard upstream/develop', { stdio: 'inherit' });
     done();
   },
+  buildTasks.cleanBuildDir,
   buildTasks.build,
+  buildTasks.checkinBuilt,
   function(done) {
     execSync('git commit -am "Rebuild"', { stdio: 'inherit' });
     execSync('git push ' + upstream_url + ' gh-pages --force', { stdio: 'inherit' });