Patches for blake3_dispatch.c to support old macOS toolchains.

1. Remove #include <immintrin.h> from the GCC path.  Nothing in the
   dispatch code uses intrinsics from that header, and it fails to
   compile on old Xcode/GCC versions that ship with OS X 10.5-10.6.

2. Encode the xgetbv instruction as raw bytes (.byte 0x0f, 0x01, 0xd0)
   instead of using the "xgetbv" mnemonic.  Assemblers bundled with
   Xcode 3.x do not recognize the mnemonic.

--- src/blake3_dispatch.c	2026-04-04 21:39:16
+++ blake3_dispatch.c.patched	2026-04-04 21:39:44
@@ -11,9 +11,7 @@
 #if defined(IS_X86)
 #if defined(_MSC_VER)
 #include <intrin.h>
-#elif defined(__GNUC__)
-#include <immintrin.h>
-#else
+#elif !defined(__GNUC__)
 #undef IS_X86 /* Unimplemented! */
 #endif
 #endif
@@ -52,7 +50,7 @@
   return _xgetbv(0);
 #else
   uint32_t eax = 0, edx = 0;
-  __asm__ __volatile__("xgetbv\n" : "=a"(eax), "=d"(edx) : "c"(0));
+  __asm__ __volatile__(".byte 0x0f, 0x01, 0xd0" : "=a"(eax), "=d"(edx) : "c"(0));
   return ((uint64_t)edx << 32) | eax;
 #endif
 }