cmd/tests: Fix "broken" handling when expected line is empty.

programs/cmd/tests/batch.c

@@ -152,6 +152,16 @@ static const char *compare_line(const char *out_line, const char *out_end, const
     static const char space_cmd[] = {'@','s','p','a','c','e','@'};
     static const char or_broken_cmd[] = {'@','o','r','_','b','r','o','k','e','n','@'};
 
+    /* Corner case where exp_line directly starts with @or_broken@, on Windowses */
+    if(broken(1)
+            && exp_line+sizeof(or_broken_cmd) <= exp_end
+            && !memcmp(exp_line, or_broken_cmd, sizeof(or_broken_cmd))) {
+        if(out_line == out_end)
+            return NULL;
+        else
+            exp_ptr = exp_line + sizeof(or_broken_cmd);
+    }
+
     while(exp_ptr < exp_end) {
         if(*exp_ptr == '@') {
             if(exp_ptr+sizeof(pwd_cmd) <= exp_end