Changes

lib/x86/cpu_features.h: drop evex512 on gcc-16

gcc-16 `master` branch dropped support for `evex512` as:
    https://gcc.gnu.org/git/?p=gcc.git;a=commitdiff;h=c052a6f4a1c803cb92147ff98fb91cf3511e0856

As a result libdeflate build started failing as:

    In file included from /build/source/lib/adler32.c:28:
    /build/source/lib/x86/adler32_template.h:135:12: error: attribute 'target' argument 'no-evex512' is unknown
      135 | ADD_SUFFIX(reduce_to_32bits)(vec_t v_s1, vec_t v_s2, u32 *s1_p, u32 *s2_p)
          |            ^~~~~~~~~~~~~~~~

The change adds upper build to `evex512` for `gcc`.
 (commit: 2a3762c)

lib/x86: drop any mention of `evex512`

`-mavx*` set of options now enable `EVEX` where
required without a separate flag. Let's drop
explicit use of `-mevex512` as it was dropped in
`gcc-16.`
 (commit: 6bb4936)