appease a few compiler warnings (-Wstrict-prototypes) (#4465)

core/iwasm/aot/aot_loader.c

@@ -4711,7 +4711,7 @@ aot_unload(AOTModule *module)
 }
 
 uint32
-aot_get_plt_table_size()
+aot_get_plt_table_size(void)
 {
     return get_plt_table_size();
 }

core/iwasm/compilation/aot.c

@@ -8,7 +8,7 @@
 static char aot_error[128];
 
 char *
-aot_get_last_error()
+aot_get_last_error(void)
 {
     return aot_error[0] == '\0' ? "" : aot_error;
 }

core/iwasm/include/aot_export.h

@@ -98,10 +98,10 @@ void
 aot_destroy_aot_file(uint8_t *aot_file);
 
 char *
-aot_get_last_error();
+aot_get_last_error(void);
 
 uint32_t
-aot_get_plt_table_size();
+aot_get_plt_table_size(void);
 
 #ifdef __cplusplus
 }