libelf: Add libeu objects to libelf.a static archive

libelf: Add libeu objects to libelf.a static archive

libelf might use some symbols from libeu.a, specifically the eu-search
wrappers. But we don't ship libeu.a separately. So include the libeu
objects in the libelf.a archive to facilitate static linking.

	* libelf/Makefile.am (libeu_objects): New variable.
	(libelf_a_LIBADD): New, add libeu_objects.

https://sourceware.org/bugzilla/show_bug.cgi?id=32293

Signed-off-by: Mark Wielaard <mark@klomp.org>