hmtx warning for variable font

[herrernst]

when trying to install the current release of the variable font (roman or italic), i get a warning about hmtx table usability on macos.

also, ttx from fonttools complains:

Dumping 'GlyphOrder' table...
Dumping 'head' table...
Dumping 'hhea' table...
Dumping 'maxp' table...
Dumping 'OS/2' table...
WARNING: too much 'hmtx' table data
Dumping 'hmtx' table...
Dumping 'cmap' table...
Dumping 'loca' table...
Dumping 'glyf' table...
Dumping 'name' table...
Dumping 'post' table...
Dumping 'BASE' table...
Dumping 'GDEF' table...
Dumping 'GPOS' table...
Dumping 'GSUB' table...
Dumping 'HVAR' table...
Dumping 'MVAR' table...
Dumping 'STAT' table...
Dumping 'avar' table...
Dumping 'fvar' table...
Dumping 'gvar' table...
Dumping 'DSIG' table...

[pauldhunt]

@herrernst I will look into this.