Add OpenBSD/arm64 support.

Signed-off-by: Kevin Lo <kevlo@kevlo.org>
Change-Id: I6f29bdb55caeec8893f128fdd50bdcc3d058cb3c
Reviewed-on: https://review.mlplatform.org/c/ml/ComputeLibrary/+/6905
Reviewed-by: Georgios Pinitas <georgios.pinitas@arm.com>
Reviewed-by: Pablo Marquez Tello <pablo.tello@arm.com>
Comments-Addressed: Pablo Marquez Tello <pablo.tello@arm.com>
Comments-Addressed: Arm Jenkins <bsgcomp@arm.com>
Tested-by: Arm Jenkins <bsgcomp@arm.com>
diff --git a/src/core/NEON/kernels/arm_gemm/transform.cpp b/src/core/NEON/kernels/arm_gemm/transform.cpp
index 60376ab..c6a3bc0 100644
--- a/src/core/NEON/kernels/arm_gemm/transform.cpp
+++ b/src/core/NEON/kernels/arm_gemm/transform.cpp
@@ -25,7 +25,9 @@
 
 #include "bfloat.hpp"
 
+#if !defined(__OpenBSD__)
 #include <alloca.h>
+#endif /* !defined(__OpenBSD__) */
 
 namespace arm_gemm {