Fix -Wimplict-int errors in configure

diff -urN a/configure b/configure
--- a/configure	2025-07-30 08:24:32.000000000 +0000
+++ b/configure	2025-12-14 23:22:38.602591014 +0000
@@ -16131,8 +16131,8 @@
             #ifdef INCLUDE_ASSERT_H
              #include <assert.h>
             #endif
-            static_assert (2 + 2 == 4, "arithmetic does not work");
-            static_assert (2 + 2 == 4);
+            int static_assert (2 + 2 == 4, "arithmetic does not work");
+            int static_assert (2 + 2 == 4);
 
 int
 main (void)
