Unify windows paths for Windows

boost::fs should be replaced by std::fs, when this is supported
For the time being we gotta stick with boost.
4 jobs for develop in 6 minutes and 21 seconds (queued for 6 seconds)
Status Job ID Name Coverage
  Configure
passed #58404
linux
configure-linux

00:00:13

 
  Compile
passed #58405
linux
make-linux

00:05:36

 
  Unit Test
passed #58406
linux
test

00:00:16

 
  Juelich Tests
failed #58407
linux
verification

00:00:15

 
Name Stage Failure
failed
verification Juelich Tests
	 25 - runtest_juelich_5 (Failed)
26 - runtest_juelich_6 (Failed)
27 - runtest_juelich_8 (Failed)
28 - runtest_juelich_9 (Failed)
Errors while running CTest
Running after script...
$ echo "End CI"
End CI
ERROR: Job failed: exit code 1