Avoid implicit declaration of atoi in CMake check. Future compilers
will not support implicit function declarations by default, so include
<stdlib.h> for a declaration of atoi.
Submitted upstream:
<https://invent.kde.org/office/calligra/-/merge_requests/81>
diff --git a/cmake/TestModernZlib.c b/cmake/TestModernZlib.c
index f7c6a0429f16b548..c9a790caaf903cbc 100644
--- a/cmake/TestModernZlib.c
+++ b/cmake/TestModernZlib.c
@@ -1,3 +1,4 @@
+#include <stdlib.h>
#include <string.h>
#include <zlib.h>