Cleanup of Dyninst build dependencies (#238)

- Refactor elfutils build folders. Move build artifacts to the "external" subfolders
- Remove reference to unused DYNINST configuration
- Declare Dyninst interfaces with other external declarations
- Updated cmake warning message
- Update the deprecation warning for "DYNINST_BUILD_${dep}" to make it clearer that the option is being translated to the new option, "ROCPROFSYS_BUILD_${dep}"

cmake/DyninstBoost.cmake

@@ -44,10 +44,6 @@
 
 include_guard(GLOBAL)
 
-# always provide Dyninst::Boost even if it is empty
-rocprofiler_systems_add_interface_library(rocprofiler-systems-boost
-                                          "Boost interface library")
-
 if(NOT BUILD_BOOST)
     find_package(Boost)
 endif()