Ignore CMAKE_SHARED_LIBRARY_<Lang>_FLAGS variable.
CMake 2.8.8 and lower compiled sources in SHARED and MODULE libraries using the value of the undocumented CMAKE_SHARED_LIBRARY_<Lang>_FLAGS platform variable. The variable contained platform-specific flags needed to compile objects for shared libraries. Typically it included a flag such as -fPIC for position independent code but also included other flags needed on certain platforms. CMake 2.8.9 and higher prefer instead to use the POSITION_INDEPENDENT_CODE target property to determine what targets should be position independent, and new undocumented platform variables to select flags while ignoring CMAKE_SHARED_LIBRARY_<Lang>_FLAGS completely.
The default for either approach produces identical compilation flags, but if a project modifies CMAKE_SHARED_LIBRARY_<Lang>_FLAGS from its original value this policy determines which approach to use.
The OLD behavior for this policy is to ignore the POSITION_INDEPENDENT_CODE property for all targets and use the modified value of CMAKE_SHARED_LIBRARY_<Lang>_FLAGS for SHARED and MODULE libraries.
The NEW behavior for this policy is to ignore CMAKE_SHARED_LIBRARY_<Lang>_FLAGS whether it is modified or not and honor the POSITION_INDEPENDENT_CODE target property.
This policy was introduced in CMake version 2.8.9. CMake version 3.9.6 warns when the policy is not set and uses OLD behavior. Use the cmake_policy command to set it to OLD or NEW explicitly.
OLD behavior of a policy is
deprecated by definition and may be removed in a future version of CMake.
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