Add libsodium to the packages, the arm build was complaining about it.

Fixup arm toolchain file.

contrib/depends/packages/packages.mk

@@ -1,4 +1,4 @@
-packages:=boost openssl libevent zeromq cppzmq zlib expat ldns cppzmq readline libiconv qt
+packages:=boost openssl libevent zeromq cppzmq zlib expat ldns cppzmq readline libiconv qt sodium
 native_packages := native_ccache
 
 wallet_packages=bdb

contrib/depends/packages/sodium.mk

@@ -0,0 +1,23 @@
+package=sodium
+$(package)_version=1.0.16
+$(package)_download_path=https://github.com/jedisct1/libsodium/archive
+$(package)_file_name=$($(package)_version).tar.gz
+$(package)_sha256_hash=0c14604bbeab2e82a803215d65c3b6e74bb28291aaee6236d65c699ccfe1a98c
+
+define $(package)_set_vars
+$(package)_config_opts=--enable-static
+$(package)_config_opts+=--prefix=$(host_prefix)
+endef
+
+define $(package)_config_cmds
+  ./autogen.sh &&\
+  $($(package)_autoconf) $($(package)_config_opts)
+endef
+
+define $(package)_build_cmds
+  $(MAKE)
+endef
+
+define $(package)_stage_cmds
+  $(MAKE) DESTDIR=$($(package)_staging_dir) install
+endef