Added include protection for unistd.h and sys/time.h.

diff --git a/dlls/ntdll/signal_sparc.c b/dlls/ntdll/signal_sparc.c
index 66f49cf..250f617 100644
--- a/dlls/ntdll/signal_sparc.c
+++ b/dlls/ntdll/signal_sparc.c
@@ -24,7 +24,9 @@
 
 #include <signal.h>
 #include <stdlib.h>
-#include <unistd.h>
+#ifdef HAVE_UNISTD_H
+# include <unistd.h>
+#endif
 #include <stdio.h>
 #include <sys/ucontext.h>