FontMake not generating names for default instance of designspace, as I expect

## Scenario

- I have a designspace for a variable font with a Weight axis from 300–800 (Light to ExtraBold)
- 300 (Light) is the default Weight value
- I am building with FontMake

## Expectation

At least in the past, I believe that the `name` table would be set up to describe the base instance of a VF, in order to describe the font adequately for legacy systems that can’t parse the `fvar` and other new tables.

So, I would expect:
- `nameID 1` Shantell Sans Light
- `nameID 2` Regular
- `nameID 3` 1.000;ARRW;ShantellSans-Light
- `nameID 4` Shantell Sans Light
- `nameID 6` ShantellSans-Light
- `nameID 16` Shantell Sans
- `nameID 17` Light

I am also getting a FontBakery `WARN`: `Subfamily name for Win is missing. It must be "Light"`. I think this is saying that name `17` should be present, and should be `Light`, as this is the base instance of the variable font.

## Reality

Instead, the font is building with names as if it had a Regular base instance:

- `nameID 1` Shantell Sans
- `nameID 2` Regular
- `nameID 3` 1.000;ARRW;ShantellSans-Regular
- `nameID 4` Shantell Sans Regular
- `nameID 6` ShantellSans-Regular
- `nameID 16` [not present]
- `nameID 17` [not present]

## Further details

FontMake version: `2.4.0`.

problem name table (Click to expand)

```xml

Weight


Light


Regular


Medium


SemiBold


Bold


ExtraBold


Copyright 2021 The Shantell Sans Project Authors (https://github.com/arrowtype/shantell-sans)


Shantell Sans


Regular


1.000;ARRW;ShantellSans-Regular


Shantell Sans Regular


Version 1.000


ShantellSans-Regular


Arrow Type


Stephen Nixon


https://arrowtype.com


https://arrowtype.com


Weight


Light


Regular


Medium


SemiBold


Bold


ExtraBold

```

Designspace (Click to expand)

```xml

com.letterror.mathModelPref
previewVarLib
com.letterror.skateboard.interactionSources

horizontal

ignore

vertical

Weight


com.letterror.skateboard.previewLocation

Weight
600.0

com.letterror.skateboard.previewText
0123456789

```

## Solution/Workaround

I think I’ve found a solution/workaround in RoboFont, by adjusting some UFO data:
- I’ve changed `openTypeNamePreferredSubfamilyName` to `Light` – it was previously was `Regular`
- I’ve set `styleMapFamilyName` to `Shantell Sans Light` – it previously wasn’t set.
- I’ve set `openTypeNamePreferredFamilyName` to `Shantell Sans` – it previously wasn’t set.

Apparent workaround in UFOs/RoboFont (Click to expand)


## Remaining question

Even though I’ve found a solution, I don’t understand it as well as I’d like. I suppose my questions become:
- When does info in a UFO override data in a designspace?
- Is there a reason the designspace data doesn’t get privileged, when it seems like this would be a simpler & more-flexible place to set name info? E.g., this would allow simpler exporting of different fonts for different reasons, without having to adjust the UFOs. This _does_ seem to work more in static builds than variable builds, which is helpful.