[#28519] build: Fix GCC 12 build

Summary:
This fixes two compile errors in GCC 12 build:

1. Error from `#pragma GCC diagnostic ignored "-Wshorten-64-to-32"` which GCC does not support. This
   pragma was changed to only be used with Clang.

2. Error from avx512fintrin.h emitting:
```
In file included from /opt/rh/gcc-toolset-12/root/usr/lib/gcc/x86_64-redhat-linux/12/include/immintrin.h:49,
                 from /opt/rh/gcc-toolset-12/root/usr/lib/gcc/x86_64-redhat-linux/12/include/x86intrin.h:32,
                 from ../../src/inline-thirdparty/hnswlib/hnswlib/hnswlib.h:34,
                 from ../../src/yb/ann_methods/hnswlib_wrapper.cc:32:
In function '__m256d _mm512_extractf64x4_pd(__m512d, int)',
    inlined from 'double _mm512_reduce_add_pd(__m512d)' at /opt/rh/gcc-toolset-12/root/usr/lib/gcc/x86_64-redhat-linux/12/include/avx512fintrin.h:16399:3,
    inlined from 'void simsimd_dot_f64_skylake(const simsimd_f64_t*, const simsimd_f64_t*, simsimd_size_t, simsimd_distance_t*)' at ../../src/inline-thirdparty/simsimd/simsimd/dot.h:1253:35:
/opt/rh/gcc-toolset-12/root/usr/lib/gcc/x86_64-redhat-linux/12/include/avx512fintrin.h:5946:10: error: '__Y' is used uninitialized [-Werror=uninitialized]
 5946 |   return (__m256d) __builtin_ia32_extractf64x4_mask ((__v8df) __A,
      |          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 5947 |                                                      __imm,
      |                                                      ~~~~~~
 5948 |                                                      (__v4df)
      |                                                      ~~~~~~~~
 5949 |                                                      _mm256_undefined_pd (),
      |                                                      ~~~~~~~~~~~~~~~~~~~~~~~
 5950 |                                                      (__mmask8) -1);
      |                                                      ~~~~~~~~~~~~~~
```

This is due to a GCC issue (https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105593) that affects
GCC 12 versions under 12.3.0. Added `-Wno-self-init` to suppress the warning for 12.x (x < 3).
Jira: DB-18208

Test Plan:
Jenkins: compile only

Jenkins run on D46343 with GCC 12 (12.2.1). Also built locally with GCC 12.3.0.

Reviewers: sergei

Reviewed By: sergei

Subscribers: yql, ybase

Tags: #jenkins-ready

Differential Revision: https://phorge.dev.yugabyte.com/D46562

Author: es1024

CMakeLists.txt

@@ -426,6 +426,11 @@ if(IS_GCC)
     # https://gist.githubusercontent.com/mbautin/de18543ea85d46db49dfa4b4b7df082a/raw
     ADD_CXX_FLAGS("-Wno-use-after-free")
   endif()
+  if ("${COMPILER_VERSION}" MATCHES "^12[.][012].*$")
+    # GCC 12 before 12.3 raises a warning due to __m256d __Y = __Y; from avxintrin.h
+    # (https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105593).
+    ADD_CXX_FLAGS("-Wno-init-self")
+  endif()
 
   # This normally gets disabled automatically (with a warning) for some files due to size of code.
   # Disable it explicitly to avoid the warning about it getting disabled automatically.

src/yb/vector_index/usearch_include_wrapper_internal.h

@@ -56,7 +56,9 @@
 #define USEARCH_USE_SIMSIMD 1
 
 #if defined(__x86_64__) || defined(_M_X64)
+#if defined(__clang__)
 #pragma GCC diagnostic ignored "-Wshorten-64-to-32"
+#endif
 
 #define SIMSIMD_TARGET_HASWELL 1
 #define SIMSIMD_TARGET_SKYLAKE 1