update release-checklist

docs/release-checklist.md

@@ -2,8 +2,12 @@
 
 on the command-line:
 
-1. update core rust submodule, if needed:
-   $ ./tools/update-core.sh
+1. a) update core rust submodule, if needed:
+      $ ./tools/update-core.sh
+
+   b) make sure, `lto = true` is present in
+      `deltachat-ios/libraries/deltachat-core-rust/Cargo.toml`
+
    depending on how much you trust in rust, you might want to do a
    ./tools/clean-core.sh before building