Install boost preprocessor header for using library use case.

Source/ThirdParty/boost/CMakeLists.txt

@@ -27,5 +27,5 @@ set (TARGET_NAME boost)
 add_custom_target (${TARGET_NAME} ALL)   # Dummy target just so that its post-build step can install headers to the build tree
 set (STATIC_LIBRARY_TARGETS ${STATIC_LIBRARY_TARGETS} ${TARGET_NAME} PARENT_SCOPE)
 
-# Install headers for building the Urho3D library
-install_header_files (DIRECTORY ./ DESTINATION ${DEST_INCLUDE_DIR}/ThirdParty/boost FILES_MATCHING PATTERN *.hpp USE_FILE_SYMLINK BUILD_TREE_ONLY)  # Note: the trailing slash is significant
+# Install headers for building and using the Urho3D library (install dependency for Urho3D/ThirdParty/AngelScript/wrap.h)
+install_header_files (DIRECTORY ./ DESTINATION ${DEST_INCLUDE_DIR}/ThirdParty/boost FILES_MATCHING PATTERN *.hpp USE_FILE_SYMLINK)  # Note: the trailing slash is significant