overlay: fix compilation with glibc

glibc fails with:
warn_unused_result [-Wunused-result]
   system("cp -a /tmp/root/upper/* / 2>/dev/null");

Regression intoroduced with 11efbf3b90f031ce634fc38cad07a4aef2985777
Reported here:
https://www.mail-archive.com/lede-dev@lists.infradead.org/msg10502.html

Signed-off-by: Roman Yeryomin <roman@advem.lv>
Acked-by: Florian Fainelli <f.fainelli@gmail.com>

diff --git a/libfstools/overlay.c b/libfstools/overlay.c
index 0187a5512d83fcd6feec2d5a0cc59321428e317d..1d69f5ac5becdebbdf4c96436003be91f6969448 100644 (file)
--- a/libfstools/overlay.c
+++ b/libfstools/overlay.c
@@ -257,7 +257,8 @@ jffs2_switch(struct volume *v)
 
                /* try hard to be in sync */
                ULOG_INFO("syncronizing overlay\n");
-               system("cp -a /tmp/root/upper/* / 2>/dev/null");
+               if (system("cp -a /tmp/root/upper/* / 2>/dev/null"))
+                       ULOG_ERR("failed to sync jffs2 overlay\n");
                break;
 
        case FS_EXT4: