Explicitly include required C headers

src/download-via-ssh/download-via-ssh.cc

@@ -9,6 +9,7 @@
 #include "store-api.hh"
 
 #include <iostream>
+#include <stdlib.h>
 #include <unistd.h>
 
 using namespace nix;

src/libmain/shared.cc

@@ -11,6 +11,7 @@
 #include <exception>
 #include <algorithm>
 
+#include <stdlib.h>
 #include <sys/time.h>
 #include <sys/stat.h>
 #include <unistd.h>

src/libstore/optimise-store.cc

@@ -4,6 +4,7 @@
 #include "local-store.hh"
 #include "globals.hh"
 
+#include <stdlib.h>
 #include <sys/types.h>
 #include <sys/stat.h>
 #include <unistd.h>

src/libstore/remote-store.cc

@@ -10,6 +10,7 @@
 #include <sys/stat.h>
 #include <sys/socket.h>
 #include <sys/un.h>
+#include <errno.h>
 #include <fcntl.h>
 
 #include <iostream>

src/libutil/monitor-fd.hh

@@ -3,6 +3,7 @@
 #include <thread>
 #include <atomic>
 
+#include <stdlib.h>
 #include <poll.h>
 #include <sys/types.h>
 #include <unistd.h>