cmake: rename temp files to avoid conflict

[junghans]

*.tmp.out seems to a cmake internal thing.

[codecov]

Codecov Report

Merging #556 into master will increase coverage by 9.3%.
The diff coverage is 70.0%.

@@           Coverage Diff            @@
##           master    #556     +/-   ##
========================================
+ Coverage    51.3%   60.6%   +9.3%     
========================================
  Files         129     124      -5     
  Lines        6118    7588   +1470     
========================================
+ Hits         3141    4603   +1462     
- Misses       2977    2985      +8     

Flag	Coverage Δ
#gcc	?

Impacted Files	Coverage Δ
include/votca/csg/bead.h	21.8% <0.0%> (-37.4%)	⬇️
include/votca/csg/beadmotif.h	100.0% <ø> (ø)
include/votca/csg/beadmotifalgorithms.h	0.0% <0.0%> (-100.0%)	⬇️
include/votca/csg/beadpair.h	85.7% <ø> (+19.0%)	⬆️
include/votca/csg/beadtriple.h	100.0% <ø> (+10.0%)	⬆️
include/votca/csg/boundarycondition.h	33.3% <0.0%> (-66.7%)	⬇️
include/votca/csg/cgengine.h	53.3% <ø> (+53.3%)	⬆️
include/votca/csg/cgmoleculedef.h	100.0% <ø> (ø)
include/votca/csg/csgapplication.h	57.8% <ø> (-42.2%)	⬇️
include/votca/csg/fileformatfactory.h	33.3% <ø> (-26.7%)	⬇️
... and 204 more

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