See https://stackoverflow.com/a/35754448
I converted the steps into a script fontforge_script.pe
To convert any font, copy the font to this directory, and run -
fontforge -script fontforge_script.pe font.ttf
If using UNIX, you may simply run -
./fontforge_script.pe font.ttf
Where font.ttf is the name of the TTF font file to convert.
After the script finishes executing, there should be a file in the same directory, called font-extra_glyphs_removed.ttf