Added some factors that affect the dependency list

Co-authored-by: Sjors Provoost <[email protected]>

doc/dependencies.md

@@ -17,6 +17,7 @@ These are the dependencies currently used by Bitcoin Core. You can find instruct
 | libevent | [2.1.8-stable](https://github.com/libevent/libevent/releases) | 2.0.22 | No |  |  |
 | libjpeg |  |  |  |  | [Yes](https://github.com/bitcoin/bitcoin/blob/master/depends/packages/qt.mk#L65) |
 | libpng |  |  |  |  | [Yes](https://github.com/bitcoin/bitcoin/blob/master/depends/packages/qt.mk#L64) |
+| libsrvg | |  |  |  |  |
 | MiniUPnPc | [2.0.20180203](http://miniupnp.free.fr/files) |  | No |  |  |
 | OpenSSL | [1.0.1k](https://www.openssl.org/source) |  | Yes |  |  |
 | PCRE |  |  |  |  | [Yes](https://github.com/bitcoin/bitcoin/blob/master/depends/packages/qt.mk#L66) |
@@ -28,3 +29,18 @@ These are the dependencies currently used by Bitcoin Core. You can find instruct
 | xkbcommon |  |  |  |  | [Yes](https://github.com/bitcoin/bitcoin/blob/master/depends/packages/qt.mk#L86) (Linux only) |
 | ZeroMQ | [4.3.1](https://github.com/zeromq/libzmq/releases) | 4.0.0 | No |  |  |
 | zlib | [1.2.11](https://zlib.net/) |  |  |  | No |
+
+Controlling dependencies
+------------------------
+Some dependencies are not needed in all configurations. The following are some factors that affect the dependency list.
+
+#### Options passed to `./configure`
+* MiniUPnPc is not needed with  `--with-miniupnpc=no`.
+* Berkeley DB is not needed with `--disable-wallet`.
+* protobuf is not needed with `--disable-bip70`.
+* Qt is not needed with `--without-gui`.
+* If the qrencode dependency is absent, QR support won't be added. To force an error when that happens, pass `--with-qrencode`.
+* ZeroMQ is needed only with the `--with-zmq` option.
+
+#### Other
+* librsvg is only needed if you need to run `make deploy` on (cross-compliation to) macOS.