Fix compilation on systems where <immintrin.h> is not available or inappropriate, such as older GCC versions or non-x86 platforms.

Author: dura0ok

src/include/storage/checksum_impl.h

@@ -112,7 +112,9 @@
 #include <cpuid.h>
 #endif
 
+#ifdef HAVE_XSAVE_INTRINSICS
 #include <immintrin.h>
+#endif
 
 #if defined(HAVE__CPUID) || defined(HAVE__CPUIDEX)
 #include <intrin.h>
@@ -253,10 +255,6 @@ pg_checksum_block_##ISANAME(const PGChecksummablePage *page) \
 }
 
 /* Declarations are always defined to make dynamic dispatch code simpler */
-
-PG_DECLARE_CHECKSUM_ISA(default);
-PG_DECLARE_CHECKSUM_ISA(avx2);
-
 PG_DEFINE_CHECKSUM_ISA(default);
 #ifdef USE_AVX2_WITH_RUNTIME_CHECK
 PG_DEFINE_CHECKSUM_ISA(avx2);