Fix logging of error messages on Windows

[bunnybot]

STDERR gets lost in windows, error messages are neither printed to console nor to the stdout.txt.

Follow-up from https://bugs.launchpad.net/widelands/+bug/1398536

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Imported from Launchpad using lp2gh.

• date created: 2018-09-14T06:43:59Z
• owner: gunchleoc
• the launchpad url was https://bugs.launchpad.net/bugs/1792521

[bunnybot]

(by klaus-halfmann)
Hmm, there is another aspect of sending this to the Homedir:

Log output will be written to: C:\Users\klaus.widelands\stdout.txt

I wanted to debug smugglers and stated two widelands instances.
To make one write to some other File I tried to use:

./widelands.exe --homedir=/mnt/d/develop/wldev/3772-1/home/

From Linux Subystem on Win 10

D:\develop\wldev\3772-1>widelands.exe --homedir=D:\develop\wldev\3772-1\home

From Windows cmd

but both give me an assertion
File: src/base/log.cc, Line 151
Expression: logger != nullptr

So how can I check the logs of both instances now?

[bunnybot]

(by gunchleoc)
If there is no stdout.txt in those directories, you can't. Please open a separate bug for it and target it to Build 20, because tis bug is about the rerouting of stderr, and your bug is about stdout.

You'll have to do your debugging with the standard homedir for now.