use Skia's pathops instead of the impressively slow booleanOperations, speeding up builds by a large factor

misc/fontbuild

@@ -216,7 +216,8 @@ class Main(object):
       [args.ufo],
       output_dir=self.tmpdir,
       output=formats,
-      subroutinize=True
+      subroutinize=True,
+      overlaps_backend='pathops', # use Skia's pathops
     )
 
     # run through ots-sanitize

requirements.txt

@@ -1,3 +1,5 @@
+skia-pathops==0.2.0.post2
+
 git+https://github.com/googlei18n/fontmake.git@db2f52a728493751a3d0446a3e281260ec9d96ff
 
 # for fontTools/varLib/interpolatable.py