crt: test: Add assert for atexit call in t_fstat

Signed-off-by: LIU Hao <lh_mouse@126.com>

mingw-w64-crt/testcases/t_fstat.c

diff --git a/mingw-w64-crt/testcases/t_fstat.c b/mingw-w64-crt/testcases/t_fstat.c
index 9500009..0a53f21 100644
--- a/mingw-w64-crt/testcases/t_fstat.c
+++ b/mingw-w64-crt/testcases/t_fstat.c
@@ -38,7 +38,7 @@
 
     strcat(dirpath, TMPTMPL);
     assert(mkdtemp(dirpath));
-    atexit(remove_dirpath);
+    assert(atexit(remove_dirpath) == 0);
     printf("mkdtemp(): path=%s\n", dirpath);
 
     handle = CreateFileA(dirpath, FILE_READ_ATTRIBUTES | DELETE, FILE_SHARE_VALID_FLAGS, NULL, OPEN_EXISTING, FILE_FLAG_BACKUP_SEMANTICS | FILE_FLAG_DELETE_ON_CLOSE, NULL);