os x從10.10更新到10.11后，原有代碼編譯報錯，#include <openssl/ssl.h>等頭文件無法找到: "openssl/ssl.h: No such file or directory".
原有環境：os x10.10+Xcode6
更新后的環境：os x10.11+Xcode7, Qt5.3.1+Qt Creator 3.3.0
解決辦法：
1.命令行執行：xcode-select —install,安裝xcode命令行工具，/usr路徑下出現include目錄 (如果原來/usr/include目錄已經存在，跳過這一步)；
/usr/include/openssl目錄里包含了相關的頭文件
2.在/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.11.sdk/usr/include/路徑下創建openssl目錄；
3.把 /usr/include/openssl路徑下的所有文件拷貝到剛建立的openssl目錄下；
原因：
os x10.11開始，蘋果sdk中不再提供openssl，在Applications/Xcode-beta.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.11.sdk/usr/include路徑下是找不到原有的openssl目錄的。
"
Sadly, it looks like we're not supposed to use it any more. As you say, it's included in the 10.10 SDK, but is deliberately missing from the 10.11 SDK.
http://lists.apple.com/archives/macnetworkprog/2015/Jun/msg00025.html
"
參考：
1.https://forums.developer.apple.com/thread/3897
2.http://stackoverflow.com/questions/14655154/mac-os-x-lion-does-not-have-usr-include-folder
另外升級后，Qt Creator中編譯會報找不到<sys/time.h>等系統頭文件，修改~/Qt5.3.1/5.3/clang_64/mkspecs/qdevice.pri文件，把macsox10.10改為macosx10.11即可以解決問題。