Try to validate filepath and warn if we can't

src/libbu/fchmod.c

@@ -156,6 +156,8 @@ bu_fchmod(int fd,
 	char filepath[MAXPATHLEN+1];
 	HANDLE h = (HANDLE)_get_osfhandle(fd);
 	GetFileNameFromHandle(h, filepath);
+	if (!bu_file_exists(filepath, NULL))
+	    bu_log("Warning:  fd %d mapped by GetFileNameFromHandle to %s, but does not exist\n", fd, filepath);
 
 	/* quell flawfinder because this is a necessary evil unless/until
 	 * someone rewrites this to use SetNamedSecurityInfo() based on