elfutils: disable for static builds

elfutils: disable for static builds

Even when doing static builds, a shared library is built. This causes a
build failure under some circumstances, for instance when building for
MIPS + uClibc + static.

After asking upstream if it would be possible to add a configure option
to not build the shared library, the answer was that doing a static
build is not a good idea. Here is a small snippet of the conversation:

"Note that fully static builds are problematic.  elfutils uses dlopen to
open the EBL backends (the CPU-specific support snippets), so even if
you link statically, the final binaries are still considerably dynamic."

Related:
  https://lists.fedorahosted.org/pipermail/elfutils-devel/2014-November/004223.html

Fixes:
  http://autobuild.buildroot.net/results/691/6913f5af6519463fbed39ef37b6a40ecf6a67b54/

Signed-off-by: Vicente Olivert Riera <Vincent.Riera@imgtec.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>