CMAKE_OSX_SYSROOT — CMake 3.10.2 Documentation

# 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.