kconf_update lost its update.log in 2014

[Harald Sitter]

...and I don't understand why

Hi!

this commit [1] wrapped KonfUpdate::log's update.log stream in `#if 0`
and thus disabling the update.log writing, replacing it with logging
to stderr instead. Why it does that eludes me though. It seems
entirely unrelated to the rest of the commit.

Should the update.log writing happen? I expect this won't be super
reliable because I think these days the application itself forks
kconf_update. If so, we should just drop the if block and update
documentation accordingly I guess (e.g. see [2])

[1] https://cgit.kde.org/kconfig.git/commit/?id=94419b6f0cd469dc7cb0184a6fb48c1fe304c4d8
[2] https://bugs.kde.org/show_bug.cgi?id=404904