Add documentation for building upstream dependencies

Fix libtinfow include

contrib/depends/toolchain.cmake.in

@@ -1,5 +1,6 @@
 cmake_minimum_required(VERSION 3.13)  # Ensure CMake version supports CMP0077
 cmake_policy(SET CMP0077 NEW)         # Ensure 'option' honors normal variables
+cmake_policy(SET CMP0148 OLD)         # Use FindPythonInterp
 
 # Set the system name to one of Android, Darwin, iOS, FreeBSD, Linux, or Windows
 SET(CMAKE_SYSTEM_NAME @depends@)
@@ -27,7 +28,7 @@ SET(ENV{PKG_CONFIG_PATH} @prefix@/lib/pkgconfig)
 SET(Readline_ROOT_DIR @prefix@)
 SET(Readline_INCLUDE_DIR @prefix@/include)
 SET(Readline_LIBRARY @prefix@/lib/libreadline.a)
-SET(Terminfo_LIBRARY @prefix@/lib/libtinfo.a)
+SET(Terminfo_LIBRARY @prefix@/lib/libtinfow.a)
 
 SET(UNBOUND_INCLUDE_DIR @prefix@/include)
 SET(UNBOUND_LIBRARIES @prefix@/lib/libunbound.a)

docs/Writerside/in.tree

@@ -14,4 +14,5 @@
         <toc-element topic="Windows.md"/>
         <toc-element topic="macOS.md"/>
     </toc-element>
+    <toc-element topic="Building-Upstream.md"/>
 </instance-profile>

docs/Writerside/topics/Building-Upstream.md

@@ -0,0 +1,35 @@
+# Building Upstream
+
+monero_c contains its own fork of contrib/depends system that is independent of monero, wownero or zano. In order to use said build system one needs to:
+
+```
+pushd contrib/depends
+env -i \
+PATH="$PATH" \
+CC=gcc CXX=g++ \
+make -j$(nproc) HOST=aarch64-apple-darwin
+popd
+```
+
+Then, get path to your desired toolchain.cmake
+
+```
+TOOLCHAIN_FILE=${PWD}/contrib/depends/aarch64-apple-darwin/share/toolchain.cmake
+```
+And finally use that as part of cmake invocation, for example to compile monero you can do the following:
+
+```
+pushd monero
+mkdir -p build/aarch64-apple-darwin
+cd $_
+cmake \
+-DCMAKE_TOOLCHAIN_FILE="$TOOLCHAIN_FILE" \
+-DBUILD_TESTS=ON \
+../..
+```
+
+From there you can build targets such as wallet_api
+
+```
+make wallet_api -j$(nproc)
+```