Appropriate fix for msys2 bot fail on gen-def.py (#894)

src/Makefile.am

@@ -243,7 +243,7 @@ DISTCLEANFILES += \
 	$(HB_GOBJECT_ENUM_headers) \
 	$(NULL)
 hb-gobject-enums.%: hb-gobject-enums.%.tmpl $(HBHEADERS)
-	$(AM_V_GEN) $(GLIB_MKENUMS) \
+	$(AM_V_GEN) PYTHONIOENCODING=UTF-8 $(GLIB_MKENUMS) \
 		--identifier-prefix hb_ --symbol-prefix hb_gobject \
 		--template $^ | \
 	sed 's/_t_get_type/_get_type/g; s/_T (/ (/g' > "$@" \

src/gen-def.py

@@ -7,7 +7,7 @@ import io, os, re, sys
 headers_content = []
 for h in os.environ["headers"].split (' '):
 	if h.endswith (".h"):
-		with io.open (h, encoding='ISO-8859-1') as f: headers_content.append (f.read ())
+		with io.open (h, encoding='utf-8') as f: headers_content.append (f.read ())
 
 result = """EXPORTS
 %s