OS X build uploading: auto-confirm SSH host key

Prevents error verifying host key (and we can't manually verify since
the prompt is obviously non-interactive).

.travis-upload.sh

@@ -24,5 +24,5 @@ if [ "$TRAVIS_BRANCH" = "master" ]; then
 
     ARCHIVE_NAME="${REV_NAME}.tar.xz"
     tar -cJvf "$ARCHIVE_NAME" "$REV_NAME"
-    lftp -c "open -u citra-builds,$BUILD_PASSWORD sftp://builds.citra-emu.org; put -O '$UPLOAD_DIR' '$ARCHIVE_NAME'"
+    lftp -c "open -u citra-builds,$BUILD_PASSWORD sftp://builds.citra-emu.org; set sftp:auto-confirm yes; put -O '$UPLOAD_DIR' '$ARCHIVE_NAME'"
 fi