Run _write_started_file() only from sage-starts

Imported from <a href="http://trac.sagemath.org/sage_trac/ticket/13988">trac #13988</a>.



Reported by: jdemeyer

Component: build

CC: 

Report Upstream: N/A

Authors: Jeroen Demeyer

Dependencies: 

Work issues: 

Reviewers: Volker Braun

Merged in: sage-5.7.beta2

Attachments: <ol><li><a href="http://trac.sagemath.org/sage_trac/attachment/ticket/13988/13988_starts_root.patch">13988_starts_root.patch: </a> by jdemeyer at 20130122T21:25:09</li><li><a href="http://trac.sagemath.org/sage_trac/attachment/ticket/13988/13988_starts_scripts.patch">13988_starts_scripts.patch: </a> by jdemeyer at 20130122T21:25:30</li><li><a href="http://trac.sagemath.org/sage_trac/attachment/ticket/13988/13988_write_started_file.patch">13988_write_started_file.patch: </a> by jdemeyer at 20130122T21:25:47</li></ol>