Fix script error when ran the first time (#90)

## 🎟️ Tracking

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point to where this change is coming from. -->

## 📔 Objective

The `rm -r ` commands would fail if those files don't exist, so the
first run of the command would immediately fail

## ⏰ Reminders before review

- Contributor guidelines followed
- All formatters and local linters executed and passed
- Written new unit and / or integration tests where applicable
- Protected functional changes with optionality (feature flags)
- Used internationalization (i18n) for all UI strings
- CI builds passed
- Communicated to DevOps any deployment requirements
- Updated any necessary documentation (Confluence, contributing docs) or
informed the documentation
  team

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crates/bitwarden-uniffi/swift/build.sh

@@ -6,10 +6,9 @@ cd "$(dirname "$0")"
 # Generate an xcframework for the Swift bindings.
 
 # Cleanup dirs
-rm -r BitwardenFFI.xcframework
-rm -r tmp
+rm -rf BitwardenFFI.xcframework
+rm -rf tmp
 
-mkdir tmp
 mkdir -p tmp/target/universal-ios-sim/release
 
 # Build native library
@@ -49,4 +48,4 @@ xcodebuild -create-xcframework \
   -output ./BitwardenFFI.xcframework
 
 # Cleanup temporary files
-rm -r tmp
+rm -rf tmp