Re: asan: more readelf leaks

In git commit fd486f32 I put some static variables used by
get_symbol_for_build_attribute in a file scope ba_cache struct.  This
was to prevent leaks in get_symbol_for_build_attribute, and to tidy up
before readelf exited.  The patch wasn't quite right though.  When
readelf processes more than one file it was possible to double free
arrays allocated in get_symbol_for_build_attribute.

	* readelf.c (process_file): Clean ba_cache.