https://bugs.gentoo.org/899012
--- a/configure.in
+++ b/configure.in
@@ -127,6 +127,7 @@ dnl AC_TRY_COMPILE("Prototypes",,extern int y(int z);y(5);}y(z)int z;{,CFLA="$CF
 
 AC_TEST_PROGRAM([
 #include <sys/time.h>
+#include <time.h>
 int main()
 {
 fd_set i,j,k ;
@@ -151,6 +152,7 @@ AC_TEST_PROGRAM([
 #include <signal.h>
 #include <stdio.h>
 #include <sys/time.h>
+#include <unistd.h>
 
 volatile int c = 0 ;
 void fct(i) int i ; { c++ ; signal(SIGALRM, fct) ; }