docs(a3k): add information about system-wide Crypto++ library

On Debian systems it is possible to use system-wide Crypto++ library.

Signed-off-by: Pali Rohár <pali@kernel.org>
Change-Id: Ib01d9376776b8afcb1ca46c16076e28c3d2e581d
diff --git a/docs/plat/marvell/armada/build.rst b/docs/plat/marvell/armada/build.rst
index 07848d3..5147cf2 100644
--- a/docs/plat/marvell/armada/build.rst
+++ b/docs/plat/marvell/armada/build.rst
@@ -317,11 +317,19 @@
         Use this parameter to point to the directory with
         compiled Crypto++ library. By default it points to the CRYPTOPP_PATH.
 
+        On Debian systems it is possible to install system-wide Crypto++ library
+        via command ``apt install libcrypto++-dev`` and specify CRYPTOPP_LIBDIR
+        to ``/usr/lib/``.
+
 - CRYPTOPP_INCDIR
 
         Use this parameter to point to the directory with
         header files of Crypto++ library. By default it points to the CRYPTOPP_PATH.
 
+        On Debian systems it is possible to install system-wide Crypto++ library
+        via command ``apt install libcrypto++-dev`` and specify CRYPTOPP_INCDIR
+        to ``/usr/include/crypto++/``.
+
 
 For example, in order to build the image in debug mode with log level up to 'notice' level run