disable custom logging when eina backtrace is active

ref 2df0404226

src/bin/e_log.c

@@ -27,8 +27,18 @@ _e_log_cb(const Eina_Log_Domain *d, Eina_Log_Level level, const char *file, cons
 EINTERN int
 e_log_init(void)
 {
+   const char *bt_level;
+
    e_log_dom = eina_log_domain_register("e", EINA_COLOR_WHITE);
-   eina_log_print_cb_set(_e_log_cb, NULL);
+   bt_level = getenv("EINA_LOG_BACKTRACE");
+   if (bt_level)
+     {
+        int level;
+
+        level = strtol(bt_level, NULL, 10);
+        if (level < 1)
+          eina_log_print_cb_set(_e_log_cb, NULL);
+     }
    return e_log_dom != -1;
 }