Add a dummy header to preserve the presence of an include directory, in order to not break downstream third-party installation logic; revert changes to CMakeLists.txt

CMakeLists.txt

@@ -11,19 +11,13 @@ project(boost_static_assert VERSION "${BOOST_SUPERPROJECT_VERSION}" LANGUAGES CX
 add_library(boost_static_assert INTERFACE)
 add_library(Boost::static_assert ALIAS boost_static_assert)
 
+target_include_directories(boost_static_assert INTERFACE include)
+
 target_link_libraries(boost_static_assert
   INTERFACE
     Boost::config
 )
 
-# Automatic installation doesn't trigger because we have no include directory
-
-if(BOOST_SUPERPROJECT_VERSION AND NOT CMAKE_VERSION VERSION_LESS 3.13)
-
-  boost_install(TARGETS boost_static_assert VERSION ${BOOST_SUPERPROJECT_VERSION})
-
-endif()
-
 # BUILD_TESTING is the standard CTest variable that enables testing
 
 if(BUILD_TESTING)

include/boost/static_assert/detail/backward.hpp

@@ -0,0 +1,12 @@
+// Copyright 2025 Peter Dimov
+// Distributed under the Boost Software License, Version 1.0.
+// https://www.boost.org/LICENSE_1_0.txt
+// 
+// This header is unused and is only present for backward compatibility.
+// Without it, StaticAssert would be the only library without an include/
+// directory, and this breaks third-party installation scripts and logic.
+
+// Introduce an artificial dependency on Config, such that libraries that
+// link to StaticAssert depend on the new location of boost/static_assert.hpp
+
+#include <boost/config.hpp>