cmake: Add MULTIPROCESS option

src/ipc/CMakeLists.txt

@@ -0,0 +1,18 @@
+# Copyright (c) 2023-present The Bitcoin Core developers
+# Distributed under the MIT software license, see the accompanying
+# file COPYING or https://opensource.org/license/mit/.
+
+add_library(bitcoin_ipc STATIC EXCLUDE_FROM_ALL
+  capnp/protocol.cpp
+  interfaces.cpp
+  process.cpp
+)
+
+target_capnp_sources(bitcoin_ipc ${PROJECT_SOURCE_DIR}
+  capnp/echo.capnp capnp/init.capnp
+)
+
+target_link_libraries(bitcoin_ipc
+  PRIVATE
+    core_interface
+)