build BUGFIX correct place where to create config.h
build BUGFIX correct place where to create config.h

Since test source files include config.h relatively, create it in
source dir instead of build dir.

PavolVican/libyang,PavolVican/libyang,PavolVican/libyang,lukasmacko/libyang,PavolVican/libyang,PavolVican/libyang,lukasmacko/libyang