Fix relocation addend sign extension on 32-bit platforms

When loading relocations on 32-bit platforms, the addend is read
as uint32 and zero-extended to uint64, which corrupts negative
addends. For example, -4 (0xFFFFFFFC) becomes 4294967292 instead
of remaining -4. Use int32 with sign extension to int64, matching
the Windows code path which already handles this correctly.

Author: sumleo

core/iwasm/aot/aot_loader.c

@@ -3868,11 +3868,12 @@ load_relocation_section(const uint8 *buf, const uint8 *buf_end,
                 read_uint64(buf, buf_end, relocation->relocation_addend);
             }
             else {
-                uint32 offset32, addend32;
+                uint32 offset32;
+                int32 addend32;
                 read_uint32(buf, buf_end, offset32);
                 relocation->relocation_offset = (uint64)offset32;
                 read_uint32(buf, buf_end, addend32);
-                relocation->relocation_addend = (uint64)addend32;
+                relocation->relocation_addend = (int64)addend32;
             }
             read_uint32(buf, buf_end, relocation->relocation_type);
             read_uint32(buf, buf_end, symbol_index);