Further cmake changes.

Add namespacing to elf find module.

Stop using CMAKE_CXX_FLAGS and start using target properties for this.

Ideally we should remove the actual option strings and replace with cmake
compiler properties or compile features.

Change-Id: I57756387b3bd3c565c99a35fed4b37fe1a2d0556


[ROCm/ROCR-Runtime commit: 9ff0268f4c]

projects/rocr-runtime/runtime/hsa-runtime/cmake_modules/FindLibElf.cmake

@@ -63,7 +63,7 @@ int main() {
 mark_as_advanced(LIBELF_INCLUDE_DIRS LIBELF_LIBRARIES ELF_GETSHDRSTRNDX)
 
 if(LIBELF_FOUND)
-  add_library(elf UNKNOWN IMPORTED)
-  set_property(TARGET elf PROPERTY IMPORTED_LOCATION ${LIBELF_LIBRARIES})
-  set_property(TARGET elf PROPERTY INTERFACE_INCLUDE_DIRECTORIES ${LIBELF_INCLUDE_DIRS})
+  add_library(elf::elf UNKNOWN IMPORTED)
+  set_property(TARGET elf::elf PROPERTY IMPORTED_LOCATION ${LIBELF_LIBRARIES})
+  set_property(TARGET elf::elf PROPERTY INTERFACE_INCLUDE_DIRECTORIES ${LIBELF_INCLUDE_DIRS})
 endif()