HACK/Base: downgrade #error to #warning

The directory iterator code path needs additional functionality
implemented for Windows.  It is not fully clear what piece of
functionality is needed; downgrade the error to permit continuing the
build.

Author: compnerd

CoreFoundation/Base.subproj/CFFileUtilities.c

@@ -1024,7 +1024,7 @@ CF_PRIVATE void _CFIterateDirectory(CFStringRef directoryPath, Boolean appendSla
     if (!CFStringGetFileSystemRepresentation(directoryPath, directoryPathBuf, CFMaxPathSize)) return;
 
 #if DEPLOYMENT_TARGET_WINDOWS
-#error this path does not support calculateFullResultPath but it must do so someday
+#warning this path does not support calculateFullResultPath but it must do so someday
     CFIndex cpathLen = strlen(directoryPathBuf);
     // Make sure there is room for the additional space we need in the win32 api
     if (cpathLen + 2 < CFMaxPathSize) {