add support for oski

bench/BenchSparseUtil.h

diff --git a/bench/BenchSparseUtil.h b/bench/BenchSparseUtil.h
index aba732d..305c70a 100644
--- a/bench/BenchSparseUtil.h
+++ b/bench/BenchSparseUtil.h
@@ -1,5 +1,4 @@
 
-#include <Eigen/Array>
 #include <Eigen/Sparse>
 #include <bench/BenchTimer.h>
 #include <set>
@@ -140,3 +139,9 @@
 
 
 #endif
+
+#ifdef OSKI
+extern "C" {
+#include <oski/oski.h>
+}
+#endif