gdb: prevent installation of libbfd.so and libopcode.so

gdb: prevent installation of libbfd.so and libopcode.so

The gdb install target installs dynamic versions of libbfd and
libopcode, accidentally overwriting the binutils provided versions
(gdb itself links against the bundled static ones to avoid
version problems, so the dynamic ones are un-needed).

Prevent the installation by using the '--disable-install-libbfd'
configure option.

Signed-off-by: Peter Seiderer <ps.report@gmx.net>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>