Fix iOS build errors on develop (#1011)

* Fix iOS

* Update changelog

Co-authored-by: Ali Abrar <ali.abrar@obsidian.systems>

ChangeLog.md

@@ -40,6 +40,7 @@ This project's release branch is `master`. This log is written from the perspect
   * [#930](https://github.com/obsidiansystems/obelisk/pull/930): Add an error to `ob run` when `static` is called with a path to a file that doesn't exist
   * [#940](https://github.com/obsidiansystems/obelisk/pull/940): Automatically restart the server when configuration is updated via `ob deploy push`.
   * [#959](https://github.com/obsidiansystems/obelisk/pull/959): Add an error to `ob run` when `staticFilePath` is called with a path to a file that doesn't exist
+  * [#1011](https://github.com/obsidiansystems/obelisk/pull/1011): Update default iOS SDK to 15.0
   * [#835](https://github.com/obsidiansystems/obelisk/pull/835): Rebuild static assets in fewer circumstances:
     * Watch `frontend`, `backend`, `common`, and `static` instead of the project root to avoid spurious rebuilds when other files change
     * Don't call `nix show-derivation` to decide whether to rebuild since it seems to do about as much work as a no-op nix-build

default.nix

@@ -1,6 +1,6 @@
 { system ? builtins.currentSystem
 , profiling ? false
-, iosSdkVersion ? "13.2"
+, iosSdkVersion ? "15.0"
 , config ? {}
 , terms ? { # Accepted terms, conditions, and licenses
     security.acme.acceptTerms = false;