LTO support broken

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The current compiler creates invalid code, if we enable LTO support. Consequently, we disable temporary the support.

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Link time optimization isn't possible between the static library OS and application because the linker uses afterwards SSE/AVX instructions in the kernel. This isn't allowed because it is possible that these instructions triggers an interrupt.

However, https://doc.rust-lang.org/cargo/reference/profiles.html#lto explains that a "thin local link time optimization" on the local crate is still possible (by setting lto to false)