Mysterious hidden .lb-file

I have all my important LaTeX-Files in a git repository. Therefore I noticed when a new hidden(!) auxiliary(?) file appeared while working on my TeX-files. The filename is .<tex-filename>.lb. Here are the facts:

• The file started to appear just recently. Because of this I guess it was caused by an update to some part of (La)TeX (I update my 2014-MacTeX-distribution roughly every week).


• I even get this on simple files (see below)


• It doesn't matter, whether I compile with XeLaTeX or pdfLaTeX


• The log file has nothing suspicious in it.

If I compile this file test.tex with pdfLaTeX:

\documentclass[10pt,a4paper]{article}
\begin{document}
Hello World!
\end{document}

I get the following .test.lb-file:

(dp0
S'engine'
p1
Vpdflatex
p2
sS'packages'
p3
c__builtin__
set
p4
((lp5
tp6
Rp7
sS'files_with_guttermarks'
p8
g4
((lp9
S'test.tex'
p10
atp11
Rp12
sS'synctex'
p13
I01
s.

Some basic informations about the file are listed and if I include some packages their names also appear in this file. The funny thing: Even the names of packages, that are not loaded (\ifXeLaTeX... \else ...) appear!

Does anybody know, what .lb-files are and what's creating them?