Background
==========
Currently Anaconda attempts to guess whether the target system's real-time clock (RTC) should be assumed to be in local time. If there is apparently a pre-existing Windows installation on the target machine, the RTC is assumed to be in local time, else in RTC.

See the function "time_initialize" in timezone.py, which ultimately relies on a set of Windows-detecting heuristics in the "is_valid_stage2_device" method of the base "BootLoader" class.

This can go wrong for a couple of reasons:
1) The heuristics are not 100% reliable in detecting a Windows install. (I've seen different results across two different machines, both of which involved Fedora being installed as a dual-boot with a pre-existing Windows 10 install.)

2) Even if Anaconda were 100% reliable in detecting Windows, the presence of a Windows install does not necessarily entail that the RTC is in local time. Windows can be configured to use an RTC in UTC.

Feature request
===============
Because some users will know for a fact whether or not the RTC is in local time, the installer UI should allow them to specify this and bypass the heuristics.

Reproducible: Sometimes

Steps to Reproduce:
1. Use Anaconda to install Fedora on a disk which has an existing Windows 10 install.
2. Boot into Fedora and execute `timedatectl` to check the setting for "RTC in local TZ"

Actual Results:
On one system, "RTC in local TZ" was "yes"; on the other it was "no".

Expected Results:
The *expected* result according to Anaconda's internal logic should have been "RTC in local TZ"=="yes" in both cases.

The *ideal* result per this feature request would have been for Anaconda to allow me to stipulate that the RTC was in UTC. Then I would have seen "RTC in local TZ"=="no" on both systems. (I had configured Windows to use a UTC RTC on both these machines.)