resulttool: Use single space indentation in json output

resulttool: Use single space indentation in json output

Using 4 space indentation in resulted in hundreds of megabytes of extra file size
in general use. Reduce this to make filesizes more managable and reduce the processing
cost. Some level of indentation and spacing does make the files more readable and allows
use of git diff so we need to retain some of it.

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>