Add linux.riscv64 precompiled support

build/linux.riscv64/Dockerfile

@@ -0,0 +1,47 @@
+FROM ubuntu:22.04
+
+ENV TARGETNAME linux.riscv64
+ENV TARGET riscv64-linux-gnu
+
+USER root
+ENV DEBIAN_FRONTEND noninteractive
+
+# Init base
+RUN apt update -y
+
+# Install qemu
+RUN apt install -y --no-install-recommends build-essential ninja-build python3 pkg-config libglib2.0-dev libpixman-1-dev curl ca-certificates python3-virtualenv
+WORKDIR /qemu
+RUN curl -Lv "https://download.qemu.org/qemu-9.0.0.tar.xz" | tar xJ --strip-components=1
+RUN ./configure --target-list=riscv64-linux-user --static --disable-system --disable-pie
+RUN cd build && ninja qemu-riscv64
+ENV QEMU_EXECVE 1
+
+
+# Set up a riscv64 userspace
+RUN apt install -y --no-install-recommends debootstrap
+RUN debootstrap --arch=riscv64 --foreign jammy /rvfs http://ports.ubuntu.com/ubuntu-ports
+RUN cp /qemu/build/qemu-riscv64 /rvfs/usr/bin/qemu-riscv64-static
+
+RUN printf > /bin/rv '%s\n' '#!/bin/sh' 'chroot /rvfs /usr/bin/qemu-riscv64-static /usr/bin/env "$@"'
+RUN chmod +x /bin/rv
+RUN [ ! -e /rvfs/debootstrap ] || rv '/debootstrap/debootstrap' --second-stage
+
+# Install deps in the chroot
+RUN printf > /rvfs/etc/apt/sources.list '%s\n' 'deb http://ports.ubuntu.com/ubuntu-ports jammy main universe'
+RUN rv apt update -y
+RUN rv apt install -y --no-install-recommends ghc cabal-install
+
+# Finally we can build the current dependencies. This takes hours.
+# jobs must be 1, GHS riscv will use about 40G memory
+RUN rv cabal update
+RUN IFS=";" && rv cabal install --dependencies-only --jobs=1 ShellCheck
+RUN IFS=';' && rv cabal install --lib --jobs=1 fgl
+
+# Clean up
+RUN rm -rf /qemu
+
+# Copy the build script
+WORKDIR /rvfs/scratch
+COPY build /rvfs/usr/bin/build
+ENTRYPOINT ["/bin/rv", "/usr/bin/build"]