build: Fix Meson warning about missing setup subcommand

WARNING: Running the setup command as `meson [options]`
instead of `meson setup [options]` is ambiguous and deprecated.

bootstrap.sh

@@ -7,7 +7,7 @@ test -d build/ && rm -r build/
 # Get external libs (MicroPython, tiny-AES-c, SHA256)
 git submodule deinit --all
 git submodule update --init ./lib
-meson --cross-file card10-cross.ini build/ "$@"
+meson setup --cross-file card10-cross.ini build/ "$@"
 
 set +x