Add ArchieSDK (Acorn Archimedes GCC 8.5.0 cross-compiler) (#127)

* Add ArchieSDK GCC cross-compiler builder

ArchieSDK provides a GCC 8.5.0 cross-compiler targeting arm-archie
(26-bit ARMv2 for Acorn Archimedes / RISC OS). Closes compiler-explorer/compiler-explorer#7982.

🤖 Generated by LLM (Claude, via OpenClaw)

* fix(archiesdk): complete build script - build toolchain from source with correct sysroot

The previous script incorrectly called './build.sh gcc' (not a supported
invocation). This replaces it with a full build that:

- Clones gcc and binutils from _targz's patched master branches
- Builds with --prefix and --with-sysroot pointing to the final CE install
  path (/opt/compiler-explorer/archiesdk/VERSION/SDK) so the baked-in
  sysroot path is correct at runtime
- Builds the SDK libraries (libc.a, libm.a, libarchie.a, crt0.o, crtheap.o)
  and installs them into the sysroot
- Tracks revisions from all three upstream repos for skip detection

🤖 Generated by LLM (Claude, via OpenClaw)

---------

Co-authored-by: mattgodbolt-molty <mattgodbolt-molty@users.noreply.github.com>

Author: mattgodbolt-molty

.github/workflows/build.yml

@@ -9,6 +9,7 @@ jobs:
     strategy:
       matrix:
         image:
+        - archiesdk
         - ccc
         - compcert
         - clad

Dockerfile.archiesdk

@@ -0,0 +1,20 @@
+FROM ubuntu:22.04
+
+ARG DEBIAN_FRONTEND=noninteractive
+RUN apt-get update -y -q && apt-get upgrade -y -q && \
+    apt-get install -y -q \
+    bison \
+    build-essential \
+    ca-certificates \
+    curl \
+    flex \
+    git \
+    texinfo \
+    wget \
+    xz-utils
+
+RUN mkdir -p /root
+COPY archiesdk /root/
+COPY common.sh /root/
+
+WORKDIR /root

archiesdk/build.sh

@@ -0,0 +1,105 @@
+#!/bin/bash
+
+## $1 : version (e.g. "Release-1")
+## $2 : destination directory
+## $3 : last revision successfully built
+
+set -ex
+source common.sh
+
+VERSION="${1}"
+LAST_REVISION="${3:-}"
+
+GCC_URL="https://gitlab.com/_targz/gcc.git"
+BINUTILS_URL="https://gitlab.com/_targz/binutils.git"
+SDK_URL="https://gitlab.com/_targz/archiesdk.git"
+
+GCC_REVISION=$(get_remote_revision "${GCC_URL}" "heads/master")
+BINUTILS_REVISION=$(get_remote_revision "${BINUTILS_URL}" "heads/master")
+SDK_REVISION=$(get_remote_revision "${SDK_URL}" "tags/${VERSION}")
+
+# Revision captures all three upstream sources
+REVISION="${VERSION}-gcc${GCC_REVISION:0:8}-bi${BINUTILS_REVISION:0:8}-sdk${SDK_REVISION:0:8}"
+
+FULLNAME="archiesdk-${VERSION}"
+OUTPUT=$(realpath "$2/${FULLNAME}.tar.xz")
+
+initialise "${REVISION}" "${OUTPUT}" "${LAST_REVISION}"
+
+# Build to the final CE install path so the sysroot baked into GCC is correct at runtime
+INSTALL_PREFIX="/opt/compiler-explorer/archiesdk/${VERSION}"
+SYSROOT="${INSTALL_PREFIX}/SDK"
+mkdir -p "${SYSROOT}/include" "${SYSROOT}/lib"
+
+NCPU=$(nproc)
+
+# Clone archiesdk at the tagged version
+git clone --depth 1 --branch "${VERSION}" "${SDK_URL}" archiesdk-src
+ARCHIESDK=$(realpath archiesdk-src)
+
+# Install SDK headers into the sysroot
+cp -r "${ARCHIESDK}/SDK/include/." "${SYSROOT}/include/"
+
+# Clone binutils and GCC from master
+git clone --depth 1 "${BINUTILS_URL}" binutils-src
+git clone --depth 1 "${GCC_URL}" gcc-src
+
+# Fetch GCC build prerequisites (gmp, mpc, mpfr, isl)
+cd gcc-src
+./contrib/download_prerequisites
+cd ..
+
+# Build binutils
+mkdir -p build-binutils
+cd build-binutils
+../binutils-src/configure \
+    --prefix="${INSTALL_PREFIX}" \
+    --target=arm-archie \
+    --with-sysroot="${SYSROOT}" \
+    --with-build-sysroot="${SYSROOT}" \
+    --disable-nls \
+    --disable-multilib
+make -j"${NCPU}" configure-host
+make -j"${NCPU}"
+make install
+cd ..
+
+# Build GCC cross-compiler + libgcc
+mkdir -p build-gcc
+cd build-gcc
+../gcc-src/configure \
+    --prefix="${INSTALL_PREFIX}" \
+    --target=arm-archie \
+    --with-sysroot="${SYSROOT}" \
+    --with-build-sysroot="${SYSROOT}" \
+    --disable-nls \
+    --disable-shared \
+    --enable-languages=c \
+    --disable-multilib \
+    --disable-threads \
+    --disable-decimal-float \
+    --disable-libgomp \
+    --disable-libmudflap \
+    --disable-libssp \
+    --disable-libatomic \
+    --disable-libquadmath \
+    --with-cpu=arm2 \
+    --with-float=soft
+make -j"${NCPU}" all-gcc all-target-libgcc \
+    CFLAGS_FOR_TARGET='-msoft-float -mcpu=arm2 -mno-thumb-interwork -O2 -ffreestanding'
+make install-gcc install-target-libgcc
+cd ..
+
+# Build SDK libraries (libc.a, libm.a, libarchie.a, crt0.o, crtheap.o)
+# Override tool paths to use our freshly built cross-compiler
+cd "${ARCHIESDK}/SDK"
+make sdk \
+    ARCHIESDK="${ARCHIESDK}" \
+    ARCHIECC="${INSTALL_PREFIX}/bin/arm-archie-gcc" \
+    ARCHIEAS="${INSTALL_PREFIX}/bin/arm-archie-as" \
+    ARCHIEAR="${INSTALL_PREFIX}/bin/arm-archie-ar" \
+    ARCHIEOBJCOPY="${INSTALL_PREFIX}/bin/arm-archie-objcopy"
+cp lib/*.a lib/*.o "${SYSROOT}/lib/"
+cd -
+
+complete "${INSTALL_PREFIX}" "${FULLNAME}" "${OUTPUT}"