[macOS, CI] Use FTP URL from environment

This URL is also subject to change, moving to Travis settings.

CI/deploy.osx.sh

@@ -6,4 +6,4 @@ DATE=`date +'%d%m%Y'`
 SHORT_COMMIT=`git rev-parse --short ${TRAVIS_COMMIT}`
 TARGET_FILENAME="OpenMW-${DATE}-${SHORT_COMMIT}.dmg"
 
-curl --ssl --ftp-create-dirs -T *.dmg -u $OSX_FTP_USER:$OSX_FTP_PASSWORD "ftp://s3.mydevil.net:21/nightly/${TARGET_FILENAME}"
+curl --ssl --ftp-create-dirs -T *.dmg -u $OSX_FTP_USER:$OSX_FTP_PASSWORD "${OSX_FTP_URL}${TARGET_FILENAME}"