doc: make -DWITH_ZMQ=ON explicit on build-unix.md

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
 
@@ -107,7 +107,7 @@ 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 dnf install zeromq-devel