Merge #15222: docs: Add info about factors that affect dependency list

55e05a8 Added some factors that affect the dependency list (Martin Erlandsson)

Pull request description:

  To simplify build instructions, the librsvg formula should be moved to the main `brew install ...` command, in my opinion.
  It is not a big problem to install a single extra formula, and it will only be unused for some users.

  An additional reason for this change is that I would like to add a comment (in a future PR) about making sure you have the latest version of all deps (in the case of preexisting formulae). That comment can be authored more clearly if this simplification PR is merged.

Tree-SHA512: e63284a4e0584f071a920f6b8ac46694de38e7b1df1e0dc2b00262c1487a2f2851fae721e8f4907a4aad0335f287e881974df6f9d05fe9b26f0ba71033dce145

Author: laanwj

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.