doc: document systemtap dependency

doc/build-unix.md

@@ -48,6 +48,7 @@ Optional dependencies:
  univalue    | Utility          | JSON parsing and encoding (bundled version will be used unless --with-system-univalue passed to configure)
  libzmq3     | ZMQ notification | Optional, allows generating ZMQ notifications (requires ZMQ version >= 4.0.0)
  sqlite3     | SQLite DB        | Optional, wallet storage (only needed when wallet enabled)
+ systemtap   | Tracing (USDT)   | Optional, statically defined tracepoints
 
 For the versions used, see [dependencies.md](dependencies.md)
 
@@ -107,6 +108,10 @@ ZMQ dependencies (provides ZMQ API):
 
     sudo apt-get install libzmq3-dev
 
+User-Space, Statically Defined Tracing (USDT) dependencies:
+
+    sudo apt install systemtap-sdt-dev
+
 GUI dependencies:
 
 If you want to build bitcoin-qt, make sure that the required packages for Qt development
@@ -162,6 +167,10 @@ ZMQ dependencies (provides ZMQ API):
 
     sudo dnf install zeromq-devel
 
+User-Space, Statically Defined Tracing (USDT) dependencies:
+
+    sudo dnf install systemtap
+
 GUI dependencies:
 
 If you want to build bitcoin-qt, make sure that the required packages for Qt development

doc/dependencies.md

@@ -24,6 +24,7 @@ These are the dependencies currently used by Bitcoin Core. You can find instruct
 | Qt | [5.12.11](https://download.qt.io/official_releases/qt/) | [5.9.5](https://github.com/bitcoin/bitcoin/issues/20104) | No |  |  |
 | SQLite | [3.32.1](https://sqlite.org/download.html) | [3.7.17](https://github.com/bitcoin/bitcoin/pull/19077) |  |  |  |
 | XCB |  |  |  |  | [Yes](https://github.com/bitcoin/bitcoin/blob/master/depends/packages/qt.mk) (Linux only) |
+| systemtap ([tracing](tracing.md))|  |  |  |  | |
 | xkbcommon |  |  |  |  | [Yes](https://github.com/bitcoin/bitcoin/blob/master/depends/packages/qt.mk) (Linux only) |
 | ZeroMQ | [4.3.1](https://github.com/zeromq/libzmq/releases) | 4.0.0 | No |  |  |
 | zlib |  |  |  |  | [Yes](https://github.com/bitcoin/bitcoin/blob/master/depends/packages/qt.mk) |
@@ -41,6 +42,7 @@ Some dependencies are not needed in all configurations. The following are some f
 * SQLite is not needed with `--disable-wallet` or `--without-sqlite`.
 * 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`.
+* If the systemtap dependency is absent, USDT support won't compiled in.
 * ZeroMQ is needed only with the `--with-zmq` option.
 
 #### Other