Fix:
conftest.c:45:5: error: implicitly declaring library function 'exit' with type 'void (int) __attribute__((noreturn))' [-Werror,-Wimplicit-function-declaration]
--- cpp/configure.orig	2011-10-03 07:57:36.000000000 -0500
+++ cpp/configure	2021-11-17 02:27:11.000000000 -0600
@@ -3973,6 +3973,7 @@
   cat confdefs.h - <<_ACEOF >conftest.$ac_ext
 /* end confdefs.h.  */
 
+#include <stdlib.h>
    int main()
    {
    #if defined(__GNUC__) && ( ( __GNUC__==2 && __GNUC_MINOR__>=8 ) || __GNUC__>=3 )
