gdb: arc: remove C++ dependency and disable build with C++

gdb: arc: remove C++ dependency and disable build with C++

gdb arc-2016.09-rc1 is based on upstream 7.12 gdb version where we can
still disable C++ build. For more information take a look at:
https://sourceware.org/gdb/wiki/cxx-conversion

We wanted to build gdb with C++ as it is used as default in 7.12
and is even a mandatory requirement since 2016/09.

But unfortunately we missed one runtime failure that C++ build causes
and so now we have to disable C++ build.

When gdb arc-2016.09-rc1 is built as a C++ application it segfaults at
runtime for ARC.

We are going to fix the issue in 2017.03 ARC toolchain release.  and
before this we remove C++ dependency are adding temporary workaround
to prevent runtime segfaults.

The workaround is to disable building gdb as C++ application via
passing --disable-build-with-cxx config option when building gdb for
ARC.

Signed-off-by: Vlad Zakharov <vzakhar@synopsys.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>