modify configuration from release to debug

Author: chupei

.travis.yml

@@ -17,8 +17,8 @@ before_script:
   - export QINIU_TEST_ENV="travis"
 
 script:
-  - xcodebuild test -workspace QiniuSDK.xcworkspace -scheme QiniuSDK_iOS -configuration Release -destination 'platform=iOS Simulator,OS=12.4,name=iPhone Xs Max' -enableCodeCoverage YES
-  - xcodebuild test -workspace QiniuSDK.xcworkspace -scheme QiniuSDK_Mac -configuration Release -destination 'platform=macOS,arch=x86_64'
+  - xcodebuild test -workspace QiniuSDK.xcworkspace -scheme QiniuSDK_iOS -configuration Debug -destination 'platform=iOS Simulator,OS=12.4,name=iPhone Xs Max' -enableCodeCoverage YES
+  - xcodebuild test -workspace QiniuSDK.xcworkspace -scheme QiniuSDK_Mac -configuration Debug -destination 'platform=macOS,arch=x86_64'
 
 after_success:
   - bash <(curl -s https://codecov.io/bash)