CMAKE_OSX_SYSROOT

Specify the location or name of the OS X platform SDK to be used. CMake uses this value to compute the value of the -isysroot flag or equivalent and to help the find_* commands locate files in the SDK.

If not set explicitly the value is initialized by the SDKROOT environment variable, if set, and otherwise computed based on the CMAKE_OSX_DEPLOYMENT_TARGET or the host platform.

The value of this variable should be set prior to the first project() or enable_language() command invocation because it may influence configuration of the toolchain and flags. It is intended to be set locally by the user creating a build tree.

This variable is ignored on platforms other than OS X.