Fix elf: Do not duplicate the GLIBC_TUNABLES string

Fix elf: Do not duplicate the GLIBC_TUNABLES string

Fix issues in sysdeps/x86/tst-hwcap-tunables.c added by

Author: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Date:   Wed Dec 6 10:24:01 2023 -0300

    elf: Do not duplicate the GLIBC_TUNABLES string

1. -AVX,-AVX2,-AVX512F should be used to disable AVX, AVX2 and AVX512.
2. AVX512 IFUNC functions check AVX512VL.  -AVX512VL should be added
to disable these functions.

This fixed:

FAIL: elf/tst-hwcap-tunables
...
[0] Spawned test for -Prefer_ERMS,-Prefer_FSRM,-AVX,-AVX2,-AVX_Usable,-AVX2_Usable,-AVX512F_Usable,-SSE4_1,-SSE4_2,-SSSE3,-Fast_Unaligned_Load,-ERMS,-AVX_Fast_Unaligned_Load
error: subprocess failed: tst-tunables
error:   unexpected output from subprocess
../sysdeps/x86/tst-hwcap-tunables.c:91: numeric comparison failure
   left: 1 (0x1); from: impls[i].usable
  right: 0 (0x0); from: false
../sysdeps/x86/tst-hwcap-tunables.c:91: numeric comparison failure
   left: 1 (0x1); from: impls[i].usable
  right: 0 (0x0); from: false
../sysdeps/x86/tst-hwcap-tunables.c:91: numeric comparison failure
   left: 1 (0x1); from: impls[i].usable
  right: 0 (0x0); from: false
../sysdeps/x86/tst-hwcap-tunables.c:91: numeric comparison failure
   left: 1 (0x1); from: impls[i].usable
  right: 0 (0x0); from: false
../sysdeps/x86/tst-hwcap-tunables.c:91: numeric comparison failure
   left: 1 (0x1); from: impls[i].usable
  right: 0 (0x0); from: false

[1] Spawned test for ,-,-Prefer_ERMS,-Prefer_FSRM,-AVX,-AVX2,-AVX_Usable,-AVX2_Usable,-AVX512F_Usable,-SSE4_1,-SSE4_2,,-SSSE3,-Fast_Unaligned_Load,,-,-ERMS,-AVX_Fast_Unaligned_Load,-,
error: subprocess failed: tst-tunables
error:   unexpected output from subprocess
../sysdeps/x86/tst-hwcap-tunables.c:91: numeric comparison failure
   left: 1 (0x1); from: impls[i].usable
  right: 0 (0x0); from: false
../sysdeps/x86/tst-hwcap-tunables.c:91: numeric comparison failure
   left: 1 (0x1); from: impls[i].usable
  right: 0 (0x0); from: false
../sysdeps/x86/tst-hwcap-tunables.c:91: numeric comparison failure
   left: 1 (0x1); from: impls[i].usable
  right: 0 (0x0); from: false
../sysdeps/x86/tst-hwcap-tunables.c:91: numeric comparison failure
   left: 1 (0x1); from: impls[i].usable
  right: 0 (0x0); from: false
../sysdeps/x86/tst-hwcap-tunables.c:91: numeric comparison failure
   left: 1 (0x1); from: impls[i].usable
  right: 0 (0x0); from: false

error: 2 test failures

on Intel Tiger Lake.