util-docker: Add docker container for building riscv target

This container comes with LLVM/Clang riscv cross-compiler
with linker, libraries, and libc headers from
riscv-gnu-toolchain[1].

Adapted from [2].

[1] https://github.com/lowRISC/riscv-llvm
[2] https://github.com/sifive/riscv-llvm/blob/dev/README.md

Signed-off-by: Hoa Nguyen <hoanguyen@ucdavis.edu>
Change-Id: I0bc310e1ae3ca9257fbde95a864c2b48009cd897
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/57609
Reviewed-by: Bobby Bruce <bbruce@ucdavis.edu>
Maintainer: Bobby Bruce <bbruce@ucdavis.edu>
Tested-by: kokoro <noreply+kokoro@google.com>

util/dockerfiles/docker-compose.yaml

@@ -110,4 +110,8 @@ services:
             args:
                 - version=12
         image: gcr.io/gem5-test/clang-version-12
-
+    llvm-gnu-cross-compiler-riscv64:
+        build:
+            context: llvm-gnu-cross-compiler-riscv64
+            dockerfile: Dockerfile
+        image: gcr.io/gem5-test/llvm-gnu-cross-compiler-riscv64

util/dockerfiles/llvm-gnu-cross-compiler-riscv64/Dockerfile

@@ -0,0 +1,74 @@
+# Copyright (c) 2022 The Regents of the University of California
+# All Rights Reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met: redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer;
+# redistributions in binary form must reproduce the above copyright
+# notice, this list of conditions and the following disclaimer in the
+# documentation and/or other materials provided with the distribution;
+# neither the name of the copyright holders nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+
+# stage 1: download the dependencies
+FROM ubuntu:20.04 AS stage1
+
+ENV DEBIAN_FRONTEND=noninteractive
+RUN apt -y update
+RUN apt -y upgrade
+RUN apt -y install \
+  binutils build-essential libtool texinfo gzip zip unzip patchutils curl git \
+  make cmake ninja-build automake bison flex gperf grep sed gawk bc \
+  zlib1g-dev libexpat1-dev libmpc-dev libglib2.0-dev libfdt-dev libpixman-1-dev
+
+# stage 2: download the compilers and compile them
+FROM stage1 AS stage2
+RUN mkdir -p /riscv/_install
+WORKDIR /riscv
+ENV PATH=`/riscv/_install/bin:$PATH`
+RUN git clone --recursive https://github.com/riscv/riscv-gnu-toolchain
+WORKDIR /riscv/riscv-gnu-toolchain
+RUN git checkout --recurse-submodules 051b9f7ddb7d136777505ea19c70a41926842b96
+RUN ./configure --prefix=/riscv/_install --enable-multilib
+RUN make linux -j`nproc`
+RUN make install
+
+WORKDIR /riscv
+RUN git clone https://github.com/llvm/llvm-project.git riscv-llvm
+WORKDIR /riscv/riscv-llvm
+RUN git checkout 2ef95efb414e215490a222de05cafdffb8054758
+RUN ln -s ../../clang llvm/tools || true
+RUN mkdir _build
+WORKDIR /riscv/riscv-llvm/_build
+RUN cmake -G Ninja -DCMAKE_BUILD_TYPE="Release" \
+  -DBUILD_SHARED_LIBS=True -DLLVM_USE_SPLIT_DWARF=True \
+  -DCMAKE_INSTALL_PREFIX="/riscv/_install" \
+  -DLLVM_OPTIMIZED_TABLEGEN=True -DLLVM_BUILD_TESTS=False \
+  -DDEFAULT_SYSROOT="/riscv/_install/sysroot" \
+  -DLLVM_DEFAULT_TARGET_TRIPLE="riscv64-unknown-linux-gnu" \
+  -DLLVM_TARGETS_TO_BUILD="RISCV" \
+  ../llvm
+RUN cmake --build . --target install -j`nproc`
+
+# stage 3: create a new container with the compiled cross-compilers only
+FROM stage1
+
+RUN mkdir -p /riscv/
+COPY --from=stage2 /riscv/_install/ /riscv/_install
+ENV PATH=/riscv/_install/bin:$PATH
+