Fix MACOSX_DEPLOYMENT_TARGET being set by distutils.spawn()

Even though a user might specify a
CMAKE_OSX_DEPLOYMENT_TARGET value, this will not automatically
set the regular MACOSX_DEPLOYMENT_TARGET environment variable,
which is picked up by the compiler to decide which standard
library to use. Because CMake is invoked via run_process ->
distutils.spawn(), spawn might decide to set its own value
of MACOSX_DEPLOYMENT_TARGET. That is undesirable.

Make sure to always specify the environment variable based on
given value, or current OS version.

(cherry picked from commit 6945dfb657a17fd66fd547e086c6fa9c76f06074)
Change-Id: I7f2dcc546c447d30fc1585cda220e3437cee9491
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@qt.io>

0 files changed, 0 insertions, 0 deletions