[subset] Update subset test suite to match some changes made to fonttools.

FontTools has added pruning functionality for code pages which we don't yet have in harfbuzz. Update our test runner to disable that for now. Also match fonttools and always recalc usFirst/LastCharIndex even if no prune unicode ranges is set.

src/hb-ot-os2-table.hh

@@ -284,12 +284,12 @@ struct OS2
         os2_prime->usWidthClass = width_class;
     }
 
-    if (c->plan->flags & HB_SUBSET_FLAGS_NO_PRUNE_UNICODE_RANGES)
-      return_trace (true);
-
     os2_prime->usFirstCharIndex = hb_min (0xFFFFu, c->plan->unicodes.get_min ());
     os2_prime->usLastCharIndex  = hb_min (0xFFFFu, c->plan->unicodes.get_max ());
 
+    if (c->plan->flags & HB_SUBSET_FLAGS_NO_PRUNE_UNICODE_RANGES)
+      return_trace (true);
+
     _update_unicode_ranges (&c->plan->unicodes, os2_prime->ulUnicodeRange);
 
     return_trace (true);

test/subset/generate-expected-outputs.py

@@ -56,6 +56,8 @@ def generate_expected_output(input_file, unicodes, profile_flags, instance_flags
 	# --gid-map is unsupported in fonttools so don't send it. Tests using
 	# it are crafted to work without fonttools knowing about the flag.
 	args.extend([f for f in profile_flags if not f.startswith("--gid-map")])
+	# Harfbuzz doesn't support pruning codepage ranges, so disable it in fonttools.
+	args.extend(["--no-prune-codepage-ranges"])
 	if not no_fonttools:
 		check_call(args)