Make faster build? Testing gftools builder "ninja" branch

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According to Simon, a "Ninja Builder" branch of gftools is theoretically a much faster way to build font files.

However, after a couple separate attempts and maybe 2–3 total hours, I have not yet succeeded in getting it to work.

Here is an (untracked) simplified designspace I recently added to the "prepped" folder to test a ninja builder config in a ninja-builder branch of this repo.

<?xml version='1.0' encoding='UTF-8'?>
<designspace format="4.1">
  <axes>
    <axis tag="wght" name="Weight" minimum="300" maximum="800" default="300"/>
  </axes>
  <sources>
    <source filename="shantell--light.ufo" familyname="Shantell Sans" stylename="Light">
      <lib copy="1"/>
      <groups copy="1"/>
      <features copy="1"/>
      <info copy="1"/>
      <location>
        <dimension name="Weight" xvalue="300"/>
      </location>
    </source>
    <source filename="shantell--extrabold.ufo" familyname="Shantell Sans" stylename="ExtraBold">
      <location>
        <dimension name="Weight" xvalue="800"/>
      </location>
    </source>
  </sources>
  <instances>
    <instance familyname="Shantell Sans Normal" stylename="Light" filename="instances/Shantell_Sans-Light.ufo">
      <location>
        <dimension name="Weight" xvalue="300"/>
      </location>
      <kerning/>
      <info/>
    </instance>
  </instances>
</designspace>

[arrowtype]

One update: running the following does run the Ninja Builder, which wasn’t even running before:

python -m gftools.builder.ninja gftools-builder-config.yaml

However, it’s still getting stuck in various ways.

[arrowtype]

The current build works well, if a little slowly, and I probably won’t need to build it a bunch more times. I may come back to this later, but for now, I’ll consider this build investigation complete.