Add Antithesis intrumentation (#5042)

* Copy Antithesis SDK version 0.4.0 to directory external/
* Add build option `voidstar` to enable instrumentation with Antithesis SDK
* Define instrumentation macros ASSERT and UNREACHABLE in terms of regular C assert
* Replace asserts with named ASSERT or UNREACHABLE
* Add UNREACHABLE to LogicError
* Document instrumentation macros in CONTRIBUTING.md

external/antithesis-sdk/CMakeLists.txt

@@ -0,0 +1,17 @@
+cmake_minimum_required(VERSION 3.25)
+
+# Note, version set explicitly by rippled project
+project(antithesis-sdk-cpp VERSION 0.4.2 LANGUAGES CXX)
+
+add_library(antithesis-sdk-cpp INTERFACE antithesis_sdk.h)
+
+# Note, both sections below created by rippled project
+target_include_directories(antithesis-sdk-cpp INTERFACE
+  $<INSTALL_INTERFACE:${CMAKE_INSTALL_INCLUDEDIR}>
+  $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}>
+)
+
+install(
+  FILES antithesis_sdk.h
+  DESTINATION "${CMAKE_INSTALL_INCLUDEDIR}"
+)