reversed outlines when building fonts from quadratic curves

We are trying to onboard a font with quadratic sources and manual hinting. The problem is that the outlines get reversed during export (as if the sources were postscript) and the manual hinting is then completely wrong.

The fonts can be build with manual hinting with gftools builder in that branch: https://github.com/RosaWagner/intel-one-mono/tree/googlefonts

This is the image the designers send after testing:

**Their build:**

**Fontmake build:**

cc @simoncozens @m4rc1e