patch UFO files with WWS entries and simplify UFO generation

Patches UFO files to contain WWS entries.
Also simplify UFO generation by moving the hard-coded make rules from the makefile into a shell script.

Related to #498 and https://github.com/googlefonts/glyphsLib/issues/820

misc/tools/postprocess_instance_ufo.py

@@ -0,0 +1,28 @@
+import sys
+import defcon
+
+def ufo_set_wws(ufo):
+  # Fix missing WWS entries for Display fonts:
+  # See https://github.com/googlefonts/glyphsLib/issues/820
+  subfamily = ufo.info.styleName
+  if subfamily.find("Display") == -1:
+    return
+  subfamily = subfamily[len("Display"):].strip()
+  if subfamily == "":
+    # "Display" -> "Regular"
+    subfamily = "Regular"
+  ufo.info.openTypeNameWWSFamilyName = "Inter Display"
+  ufo.info.openTypeNameWWSSubfamilyName = subfamily
+
+
+def main(argv):
+  ufo_file = argv[1]
+  if ufo_file.find("Display") == -1:
+    return  # skip fonts of "default" family
+  ufo = defcon.Font(ufo_file)
+  ufo_set_wws(ufo)
+  ufo.save(ufo_file)
+
+
+if __name__ == '__main__':
+  main(sys.argv)