[sysprof] preload: use #ifdef, not #if ENABLE_LIBUNWIND

[Christian Hergert <chergert src gnome org>]

commit b0157683ef1e09d95d34d1800f65e3392156f797
Author: Christian Hergert <chergert redhat com>
Date:   Thu Feb 20 11:04:32 2020 -0800

    preload: use #ifdef, not #if ENABLE_LIBUNWIND

 src/libsysprof/preload/sysprof-memory-collector.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/src/libsysprof/preload/sysprof-memory-collector.c 
b/src/libsysprof/preload/sysprof-memory-collector.c
index 6e1c632..33b1d0e 100644
--- a/src/libsysprof/preload/sysprof-memory-collector.c
+++ b/src/libsysprof/preload/sysprof-memory-collector.c
@@ -62,7 +62,7 @@ G_DEFINE_CONSTRUCTOR(collector_init_ctor)
 static void
 collector_init_ctor (void)
 {
-#if ENABLE_LIBUNWIND
+#ifdef ENABLE_LIBUNWIND
   unw_set_caching_policy (unw_local_addr_space, UNW_CACHE_PER_THREAD);
   unw_set_cache_size (unw_local_addr_space, 1024, 0);
 #endif