scripts: use UTF-8 for API XML files

The build system will be running in UTF-8 locale, so any content in the
API XML files will also end up being UTF-8, not ISO-8859-1.
Reviewed-by: NMichal Privoznik <mprivozn@redhat.com>
Signed-off-by: NDaniel P. Berrangé <berrange@redhat.com>

scripts/apibuild.py

@@ -2333,7 +2333,7 @@ class docBuilder:
         if not quiet:
             print("Saving XML description %s" % (filename))
         output = open(filename, "w")
-        output.write('<?xml version="1.0" encoding="ISO-8859-1"?>\n')
+        output.write('<?xml version="1.0" encoding="UTF-8"?>\n')
         output.write("<api name='%s'>\n" % self.name)
         output.write("  <files>\n")
         headers = sorted(self.headers.keys())