ARC: Add multilib support for linux targets

We used to build baremetal (AKA Elf32) multilibbed toolchains for years
now but never made that for Linux targets since there were problems with
uClibc n multilib setup. Now with help of Crosstool-NG it is finally
possible to create uClibc-based multilibbed toolchains and so we add
relevant CPUs for multilib in case of configuration for "arc*-*-linux*".

This will be essentially useful for glibc-based multilibbbed toolchains
in the future.

gcc/
2018-05-16  Alexey Brodkin <abrodkin@synopsys.com>

        * config.gcc: Add arc/t-multilib-linux to tmake_file for
        arc*-*-linux*.
        * config/arc/t-multilib-linux: Specify MULTILIB_OPTIONS and
        MULTILIB_DIRNAMES
---
 gcc/config.gcc                  |  2 +-
 gcc/config/arc/t-multilib-linux | 25 +++++++++++++++++++++++++
 2 files changed, 26 insertions(+), 1 deletion(-)
 create mode 100644 gcc/config/arc/t-multilib-linux

* Alexey Brodkin <Alexey.Brodkin@synopsys.com> [2018-05-16 22:42:36 +0300]:

> We used to build baremetal (AKA Elf32) multilibbed toolchains for years
> now but never made that for Linux targets since there were problems with
> uClibc n multilib setup. Now with help of Crosstool-NG it is finally
> possible to create uClibc-based multilibbed toolchains and so we add
> relevant CPUs for multilib in case of configuration for "arc*-*-linux*".
> 
> This will be essentially useful for glibc-based multilibbbed toolchains
> in the future.
> 
> gcc/
> 2018-05-16  Alexey Brodkin <abrodkin@synopsys.com>
> 
>         * config.gcc: Add arc/t-multilib-linux to tmake_file for
>         arc*-*-linux*.
>         * config/arc/t-multilib-linux: Specify MULTILIB_OPTIONS and
>         MULTILIB_DIRNAMES

Looks good.

Thanks,
Andrew

> ---
>  gcc/config.gcc                  |  2 +-
>  gcc/config/arc/t-multilib-linux | 25 +++++++++++++++++++++++++
>  2 files changed, 26 insertions(+), 1 deletion(-)
>  create mode 100644 gcc/config/arc/t-multilib-linux
> 
> diff --git a/gcc/config.gcc b/gcc/config.gcc
> index a5defb0f0058..8e038a72f613 100644
> --- a/gcc/config.gcc
> +++ b/gcc/config.gcc
> @@ -1059,7 +1059,7 @@ arc*-*-elf*)
>  	;;
>  arc*-*-linux*)
>  	tm_file="arc/arc-arch.h dbxelf.h elfos.h gnu-user.h linux.h linux-android.h glibc-stdint.h arc/linux.h ${tm_file}"
> -	tmake_file="${tmake_file} arc/t-arc"
> +	tmake_file="${tmake_file} arc/t-multilib-linux arc/t-arc"
>  	extra_gcc_objs="driver-arc.o"
>  	if test "x$with_cpu" != x; then
>  		tm_defines="${tm_defines} TARGET_CPU_BUILD=PROCESSOR_$with_cpu"
> diff --git a/gcc/config/arc/t-multilib-linux b/gcc/config/arc/t-multilib-linux
> new file mode 100644
> index 000000000000..f357cfc3f926
> --- /dev/null
> +++ b/gcc/config/arc/t-multilib-linux
> @@ -0,0 +1,25 @@
> +# Copyright (C) 2018 Free Software Foundation, Inc.
> +#
> +# This file is part of GCC.
> +#
> +# GCC is free software; you can redistribute it and/or modify it under
> +# the terms of the GNU General Public License as published by the Free
> +# Software Foundation; either version 3, or (at your option) any later
> +# version.
> +#
> +# GCC is distributed in the hope that it will be useful, but WITHOUT ANY
> +# WARRANTY; without even the implied warranty of MERCHANTABILITY or
> +# FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
> +# for more details.
> +#
> +# You should have received a copy of the GNU General Public License
> +# along with GCC; see the file COPYING3.  If not see
> +# <http://www.gnu.org/licenses/>.
> +
> +MULTILIB_OPTIONS = mcpu=hs/mcpu=archs/mcpu=hs38/mcpu=hs38_linux/mcpu=arc700/mcpu=nps400
> +
> +MULTILIB_DIRNAMES = hs archs hs38 hs38_linux arc700 nps400
> +
> +# Aliases:
> +MULTILIB_MATCHES += mcpu?arc700=mA7
> +MULTILIB_MATCHES += mcpu?arc700=mARC700
> -- 
> 2.17.0
>

Pushed.

Thank you for your contribution,
Claudiu