tools/elfutils: override SUBDIRS variable of Makefile

tools/elfutils: override SUBDIRS variable of Makefile

Instead of editing the SUBDIRS variable with a patch, it can be overriden
at the end of the command line when invoking Make.

This tool has a series of recursive Makefiles in each subdirectory,
therefore SUBDIRS is set to a pattern of Make functions so that the result
is variable depending on the current subdirectory that Make is being
invoked in.

It's not necessary to have gnulib-cache.m4 in EXTRA_DIST since we don't
need to re-import after packaging this in the SDK, so get rid of the
entire patch hunk for ./Makefile.am

Tested-by: Georgi Valkov <gvalkov@gmail.com> # MacOS
Signed-off-by: Michael Pratt <mcpratt@pm.me>
Signed-off-by: Tony Ambardar <itugrok@yahoo.com>