Fix Mac build.

Not sure how this built on Linux, the correct type is siginfo_t and
we use that correctly elsewhere.

Change-Id: I44ddc77e11558337342c1448553a16c7db231a66
diff --git a/runtime/instruction_set.cc b/runtime/instruction_set.cc
index b5f8571..0ca32fe 100644
--- a/runtime/instruction_set.cc
+++ b/runtime/instruction_set.cc
@@ -16,6 +16,7 @@
 
 #include "instruction_set.h"
 
+#include <signal.h>
 #include <fstream>
 
 #include "base/casts.h"
@@ -430,7 +431,7 @@
 // A signal handler called by a fault for an illegal instruction.  We record the fact in r0
 // and then increment the PC in the signal context to return to the next instruction.  We know the
 // instruction is an sdiv (4 bytes long).
-static void bad_divide_inst_handle(int signo, siginfo *si, void *data) {
+static void bad_divide_inst_handle(int signo, siginfo_t* si, void* data) {
   UNUSED(signo);
   UNUSED(si);
 #if defined(__arm__)