Move `GC_CAN_COMPILE_COMPACTION` definition before used

gc.c

@@ -327,6 +327,14 @@ rb_gc_guarded_ptr_val(volatile VALUE *ptr, VALUE val)
 #define GC_OLDMALLOC_LIMIT_MAX (128 * 1024 * 1024 /* 128MB */)
 #endif
 
+#ifndef GC_CAN_COMPILE_COMPACTION
+#if defined(__wasi__) /* WebAssembly doesn't support signals */
+# define GC_CAN_COMPILE_COMPACTION 0
+#else
+# define GC_CAN_COMPILE_COMPACTION 1
+#endif
+#endif
+
 #ifndef PRINT_MEASURE_LINE
 #define PRINT_MEASURE_LINE 0
 #endif
@@ -2249,6 +2257,7 @@ heap_assign_page(rb_objspace_t *objspace, rb_size_pool_t *size_pool, rb_heap_t *
     heap_add_freepage(heap, page);
 }
 
+#if GC_CAN_COMPILE_COMPACTION
 static void
 heap_add_pages(rb_objspace_t *objspace, rb_size_pool_t *size_pool, rb_heap_t *heap, size_t add)
 {
@@ -2262,6 +2271,7 @@ heap_add_pages(rb_objspace_t *objspace, rb_size_pool_t *size_pool, rb_heap_t *he
 
     GC_ASSERT(size_pool->allocatable_pages == 0);
 }
+#endif
 
 static size_t
 minimum_pages_for_size_pool(rb_objspace_t *objspace, int size_pool_idx)
@@ -5183,14 +5193,8 @@ gc_unprotect_pages(rb_objspace_t *objspace, rb_heap_t *heap)
 }
 
 static void gc_update_references(rb_objspace_t * objspace);
+#if GC_CAN_COMPILE_COMPACTION
 static void invalidate_moved_page(rb_objspace_t *objspace, struct heap_page *page);
-
-#ifndef GC_CAN_COMPILE_COMPACTION
-#if defined(__wasi__) /* WebAssembly doesn't support signals */
-# define GC_CAN_COMPILE_COMPACTION 0
-#else
-# define GC_CAN_COMPILE_COMPACTION 1
-#endif
 #endif
 
 #if defined(__MINGW32__) || defined(_WIN32)
@@ -5879,6 +5883,7 @@ gc_sweep_continue(rb_objspace_t *objspace, rb_size_pool_t *sweep_size_pool, rb_h
     gc_sweeping_exit(objspace);
 }
 
+#if GC_CAN_COMPILE_COMPACTION
 static void
 invalidate_moved_plane(rb_objspace_t *objspace, struct heap_page *page, uintptr_t p, bits_t bitset)
 {
@@ -5951,6 +5956,7 @@ invalidate_moved_page(rb_objspace_t *objspace, struct heap_page *page)
         p += BITS_BITLENGTH * BASE_SLOT_SIZE;
     }
 }
+#endif
 
 static void
 gc_compact_start(rb_objspace_t *objspace)