Enable interprocedural optimization for a target.
If set to true, enables interprocedural optimizations if they are
to be supported by the compiler. Depending
on value of policy
CMP0069, the error will be reported or ignored,
if interprocedural optimization is enabled but not supported.
This property is initialized by the
CMAKE_INTERPROCEDURAL_OPTIMIZATION variable if it is set when a
target is created.
There is also the per-configuration
target property, which overrides
if it is set.