Mojo: Improve my mojob script.

Handle different "configuration" options in a more reasonable way. Add the
ability to make shared_library component builds (and make that the default).
(Also set use_aura=1 unconditionally.)

R=darin
NOTRY=True

Review URL: https://codereview.chromium.org/82193003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@236704 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 236704