Add iOS build task

.travis.yml

@@ -58,10 +58,13 @@ matrix:
       install:
         - rustup target add aarch64-apple-ios armv7-apple-ios armv7s-apple-ios x86_64-apple-ios i386-apple-ios
         - cargo install --git https://github.com/TimNN/cargo-lipo
+        - gem install xcode-install
+        - instruments -s devices
       script:
-        - cd ffi
-        - cargo lipo --release
-        - cd ..
+        - >
+          cd ffi &&
+          cargo lipo --release &&
+          cd ..
         - cd sdks/swift/Mentat
         - xcodebuild -configuration Debug -scheme "Mentat Debug" -sdk iphonesimulator test -destination 'platform=iOS Simulator,name=iPhone X,OS=11.4' | xcpretty
         - cd ../../..