Merge bitcoin/bitcoin#32696: doc: make -DWITH_ZMQ=ON explicit on build-unix.md

32d4e92 doc: make `-DWITH_ZMQ=ON` explicit on `build-unix.md` (Luis Schwab)

Pull request description:

  ZMQ support is not built by default on Linux, and the docs don't make that clear. This PR makes it explicit that the `-DWITH_ZMQ=ON` flag is required to build with ZMQ support on `build-unix.md`.

ACKs for top commit:
  maflcko:
    lgtm ACK 32d4e92

Tree-SHA512: 322d0dd86bb80aa5a5640a5510cbeeec29f490c33b8f7360e3a202147a02c303064e6761ceb42e38e26982c61f35c9b048804c705a0d95c5737ebd2109febead

Author: fanquake

doc/build-unix.md

@@ -56,7 +56,7 @@ SQLite is required for the descriptor wallet:
 
 To build Bitcoin Core without wallet, see [*Disable-wallet mode*](#disable-wallet-mode)
 
-ZMQ dependencies (provides ZMQ API):
+ZMQ-enabled binaries are compiled with `-DWITH_ZMQ=ON` and require the following dependency:
 
     sudo apt-get install libzmq3-dev
 
@@ -107,15 +107,15 @@ SQLite is required for the descriptor wallet:
 
 To build Bitcoin Core without wallet, see [*Disable-wallet mode*](#disable-wallet-mode)
 
-ZMQ dependencies (provides ZMQ API):
+ZMQ-enabled binaries are compiled with `-DWITH_ZMQ=ON` and require the following dependency:
 
     sudo dnf install zeromq-devel
 
 User-Space, Statically Defined Tracing (USDT) dependencies:
 
     sudo dnf install systemtap-sdt-devel
 
-IPC-enabled binaries are compiled  with `-DENABLE_IPC=ON` and require the following dependency.
+IPC-enabled binaries are compiled with `-DENABLE_IPC=ON` and require the following dependency.
 Skip if you do not need IPC functionality.
 
     sudo dnf install capnproto