build: set wrap_mode=nodownload in default options

This can be surprising (e.g. in CI, this can download source code
instead of using system libraries) and users can easily turn it
back on if desired.

meson.build

@@ -8,6 +8,7 @@ project(
 		'c_std=c11',
 		'warning_level=2',
 		'werror=true',
+		'wrap_mode=nodownload',
 	],
 )