Build: Add LLVM toolchain support for an521 only.

Support for other platforms will follow.

Signed-off-by: Anton Komlev <anton.komlev@arm.com>
Change-Id: Id036ecd78bf8e8909af30f78b2bfe5262b78c6b9
diff --git a/secure_fw/include/security_defs.h b/secure_fw/include/security_defs.h
index a048356..a5929d4 100644
--- a/secure_fw/include/security_defs.h
+++ b/secure_fw/include/security_defs.h
@@ -21,6 +21,12 @@
 /* Attributes for psa api secure gateway functions */
 #if defined(__GNUC__) && !defined(__ARMCC_VERSION)
 /*
+ * LLVM offers 'noduplicate' attribute as 'noclone' equivalent in GNUARM
+ */
+#if defined(__clang__)
+#define noclone noduplicate
+#endif /* __clang__ */
+/*
  * GNUARM requires noclone attribute to protect gateway function symbol from
  * being renamed and cloned
  */