OS X CMake isysroot notes

The issue described here with the effect that: CMake always adds -isysroot explicitly to get the macosx SDK. This behaviour that was once required to get anything to compile on the command line. One can see that the flag affects whether /usr/local/include is considered an implicit include directory by the compiler

Unfortunately, unsetting the CMAKE_OSX_SYSROOT like so -DCMAKE_OSX_SYSROOT="/" does not work as it affects the FindOpenGL.cmake modules ability to find OpenGL.

Setting the following env variable prior to running cmake does work. export CXXFLAGS=-isystem\ /usr/local/include