Could You please help me with this. I've tried attaching the project zip but I'm not allowed to do so.

The funny thing is that once the board.txt file is added to project dir, no log will be written in dir BlinkStm32\Debug\logs\gdb\. But it will write logs with no board.txt file added to project.

Thanks.

To summarize what I have done so far:
All files are UTF-8 encoded, Windows EOL carriages

1) I have added file 
...\VisualStudio\...\tools\openocd-0.9.0\scripts\board\stm32f103c8t6mini.cfg
with content from your post in this thread

2) I have added the board.txt file in project dir with content which can be found in attachment

3) I have tried to hard-code all the paths inside board.txt file with no success

4) Without the board.txt file odb creates log file inside Debug dir but with board.txt file it will not create any log

5) I've verified that openocd runs with the created config file:
in a cmd:

bin\openocd.exe -f scripts\board\stm32f103c8t6mini.cfg 

and device connected

than in another cmd:

telnet localhost 4444
> reset halt
> flash probe 0
> stm32f1x mass_erase 0
> reset halt
 

and everything went smoothly

I think this should be the short version of attempts I have done so far.

Thanks.