libffi: Update to version 3.4.7

libffi: Update to version 3.4.7

- Update from version 3.4.6 to 3.4.7
- Update of rootfile not required
- Changelog
    3.4.7
        Add static trampoline support for Linux on s390x.
        Fix BTI support for ARM64.
        Support pointer authentication for ARM64.
        Fix ASAN compatibility.
        Fix x86-64 calls with 6 GP registers and some SSE registers.
        Miscellaneous fixes for ARC and Darwin ARM64.
        Fix OpenRISC or1k and Solaris 10 builds.
        Remove nios2 port.

Signed-off-by: Adolf Belka <adolf.belka@ipfire.org>
Signed-off-by: Michael Tremer <michael.tremer@ipfire.org>