Update file ForwardDeclarations.h

Eigen/src/Core/util/ForwardDeclarations.h

diff --git a/Eigen/src/Core/util/ForwardDeclarations.h b/Eigen/src/Core/util/ForwardDeclarations.h
index 7f178b9..facb074 100644
--- a/Eigen/src/Core/util/ForwardDeclarations.h
+++ b/Eigen/src/Core/util/ForwardDeclarations.h
@@ -254,7 +254,7 @@
 template<typename MatrixType,int RowFactor,int ColFactor> class Replicate;
 template<typename MatrixType, int Direction = BothDirections> class Reverse;
 
-#if defined(EIGEN_USE_LAPACKE)
+#if defined(EIGEN_USE_LAPACKE) && defined(lapack_int)
 // Lapacke interface requires StorageIndex to be lapack_int
 typedef lapack_int DefaultPermutationIndex;
 #else