meson: add missing final newline in jinja2 outputs

I think this might be caused by trim_blocks=True. We were
missing the final newline everywhere.

tools/meson-render-jinja2.py

@@ -31,5 +31,6 @@ if __name__ == '__main__':
     output = render(sys.argv[2], defines)
     with open(sys.argv[3], 'w') as f:
         f.write(output)
+        f.write('\n')
     info = os.stat(sys.argv[2])
     os.chmod(sys.argv[3], info.st_mode)