fix xcode crash in travis-ci

Author: tapashmajumder

.travis.yml

@@ -1,11 +1,11 @@
-osx_image: xcode10
+osx_image: xcode10.2
 language: swift
 
 before_install:
   - gem install xcpretty xcpretty-travis-formatter
 
 script:
-  - xcodebuild test -workspace swift-sdk.xcworkspace -scheme swift-sdk -sdk iphonesimulator -destination 'platform=iOS Simulator,name=iPhone X' -enableCodeCoverage YES CODE_SIGNING_REQUIRED=NO GCC_INSTRUMENT_PROGRAM_FLOW_ARCS=YES GCC_GENERATE_TEST_COVERAGE_FILES=YES | xcpretty -f `xcpretty-travis-formatter`
+  - xcodebuild test -workspace swift-sdk.xcworkspace -scheme swift-sdk -sdk iphonesimulator -destination 'platform=iOS Simulator,name=iPhone Xs' -enableCodeCoverage YES CODE_SIGNING_REQUIRED=NO GCC_INSTRUMENT_PROGRAM_FLOW_ARCS=YES GCC_GENERATE_TEST_COVERAGE_FILES=YES | xcpretty -f `xcpretty-travis-formatter`
   - bash <(curl -s https://codecov.io/bash)
   - xcodebuild test -workspace swift-sdk.xcworkspace -scheme ios9-tests -sdk iphonesimulator -destination 'platform=iOS Simulator,name=iPhone 6s,OS=9.0' -enableCodeCoverage YES CODE_SIGNING_REQUIRED=NO GCC_INSTRUMENT_PROGRAM_FLOW_ARCS=YES GCC_GENERATE_TEST_COVERAGE_FILES=YES | xcpretty -f `xcpretty-travis-formatter`
   - bash <(curl -s https://codecov.io/bash)