Fix build problem on sparc


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@5428 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Support/SystemUtils.cpp b/lib/Support/SystemUtils.cpp
index 98b2fc6..034c141f 100644
--- a/lib/Support/SystemUtils.cpp
+++ b/lib/Support/SystemUtils.cpp
@@ -9,7 +9,8 @@
 #include <algorithm>
 #include <fstream>
 #include <iostream>
-#include <stdlib.h>
+#include <cstdlib>
+#include <alloca.h>
 #include <sys/types.h>
 #include <sys/stat.h>
 #include <fcntl.h>