CI: Add a LTO/IPO build

[chfast]

Add a LTO build to CI. We can check the performance of Release vs Release+LTO builds but previously difference where neglectable. However, LTO build can reveal some C++ bugs.

In CMake IPO can be enabled with INTERPROCEDURAL_OPTIMIZATION property. The Hunter controlled dependencies should be build with IPO enabled too therefore a CMake toolchain file must be used.

[sofiqul60]

need a job

[Uglybutlikable]

nice