compiler AVX2 intrinsics check is failing in autotools.

[sezero]

This is on i686-linux with gcc-14. Relevant parts of config.log:

configure:15283: checking if compiler supports AVX2 intrinsics with -mavx -mfma -mavx2
configure:15312: gcc14 -o conftest -g -O2 -mavx -mfma -mavx2   conftest.c  >&5
conftest.c: In function 'main':
conftest.c:40:53: error: passing argument 1 of '_mm_loadu_si128' from incompatible pointer type [-Wincompatible-pointer-types]
   40 |               _mm256_cvtepi16_epi32(_mm_loadu_si128(utest));
      |                                                     ^~~~~
      |                                                     |
      |                                                     unsigned char *
In file included from /opt/gcc14/lib/gcc/i686-pc-linux-gnu/14.1.1/include/xmmintrin.h:1322,
                 from /opt/gcc14/lib/gcc/i686-pc-linux-gnu/14.1.1/include/immintrin.h:31,
                 from conftest.c:25:
/opt/gcc14/lib/gcc/i686-pc-linux-gnu/14.1.1/include/emmintrin.h:704:35: note: expected 'const __m128i_u *' but argument is of type 'unsigned char *'
  704 | _mm_loadu_si128 (__m128i_u const *__P)
      |                  ~~~~~~~~~~~~~~~~~^~~
configure:15312: $? = 1
configure: failed program was:
| /* confdefs.h */
| #define PACKAGE_NAME "opus"
| #define PACKAGE_TARNAME "opus"
| #define PACKAGE_VERSION "1.5.2-12-gfc96bb9"
| #define PACKAGE_STRING "opus 1.5.2-12-gfc96bb9"
| #define PACKAGE_BUGREPORT "opus@xiph.org"
| #define PACKAGE_URL ""
| #define HAVE_STDIO_H 1
| #define HAVE_STDLIB_H 1
| #define HAVE_STRING_H 1
| #define HAVE_INTTYPES_H 1
| #define HAVE_STDINT_H 1
| #define HAVE_STRINGS_H 1
| #define HAVE_SYS_STAT_H 1
| #define HAVE_SYS_TYPES_H 1
| #define HAVE_UNISTD_H 1
| #define STDC_HEADERS 1
| #define HAVE_DLFCN_H 1
| #define LT_OBJDIR ".libs/"
| #define OPUS_BUILD /**/
| #define restrict __restrict
| #define VAR_ARRAYS 1
| #define FLOAT_APPROX 1
| /* end confdefs.h.  */
| #include <immintrin.h>
|            #include <time.h>
| 
| int
| main (void)
| {
| 
|              unsigned char utest[16] = {1};
|              __m256 mtest;
|              __m256i mtest1;
|              __m256i mtest2;
|              mtest = _mm256_set1_ps((float)time(NULL));
|              mtest = _mm256_fmadd_ps(mtest, mtest, mtest);
|              mtest1 = _mm256_set_m128i(_mm_loadu_si64(utest), _mm_loadu_si64(utest));
|              mtest2 =
|               _mm256_cvtepi16_epi32(_mm_loadu_si128(utest));
|              return _mm256_extract_epi16(_mm256_xor_si256(
|               _mm256_xor_si256(mtest1, mtest2), _mm256_cvttps_epi32(mtest)), 0);
| 
| 
|   ;
|   return 0;
| }
configure:15321: result: no
configure:15445: WARNING: Compiler does not support AVX2 intrinsics