Add dependency to cprover_library.inc for the C++ module

This ensures that the library is actually built (and therefore used) by
the C++ frontend (otherwise, the CMake version never genreates
cprover_library.inc and the C version of the file is imported twice.

Also mirrored the changes made in the ansi-c CMakeLists.txt which
detects changes in the source of the library

Author: Thomas Kiley

src/cpp/CMakeLists.txt

@@ -1,14 +1,8 @@
 file(GLOB cpp_library_sources "library/*.c")
 
-add_custom_command(OUTPUT converter_input.txt
-    COMMAND cat ${cpp_library_sources} > converter_input.txt
-    DEPENDS ${cpp_library_sources}
-)
-
 add_custom_command(OUTPUT "${CMAKE_CURRENT_BINARY_DIR}/cprover_library.inc"
-    COMMAND ../ansi-c/converter < "converter_input.txt" > "${CMAKE_CURRENT_BINARY_DIR}/cprover_library.inc"
-    DEPENDS "converter_input.txt" ../ansi-c/converter
-)
+        COMMAND cat ${cpp_library_sources} | $<TARGET_FILE:converter> > "${CMAKE_CURRENT_BINARY_DIR}/cprover_library.inc"
+        DEPENDS converter ${cpp_library_sources})
 
 ################################################################################
 
@@ -33,6 +27,12 @@ endif()
 file(GLOB_RECURSE sources "*.cpp" "*.h")
 add_library(cpp ${sources})
 
+set_source_files_properties(
+        ${sources}
+        PROPERTIES
+        OBJECT_DEPENDS "${CMAKE_CURRENT_BINARY_DIR}/cprover_library.inc"
+)
+
 generic_includes(cpp)
 
 target_link_libraries(cpp util ansi-c)