Fix CI for riscv64-unknown-linux-gnu

Author: Amanieu

.github/workflows/main.yml

@@ -168,6 +168,8 @@ jobs:
           os: ubuntu-latest
         - target: thumbv7em-none-eabihf
           os: ubuntu-latest
+        - target: riscv64gc-unknown-linux-gnu
+          os: ubuntu-latest
 
     steps:
     - uses: actions/checkout@master

ci/docker/riscv64gc-unknown-linux-gnu/Dockerfile

@@ -0,0 +1,10 @@
+FROM ubuntu:21.10
+
+RUN apt-get update && apt-get install -y --no-install-recommends \
+        gcc libc6-dev qemu-user ca-certificates \
+        gcc-riscv64-linux-gnu libc6-dev-riscv64-cross \
+        qemu-user
+
+ENV CARGO_TARGET_RISCV64GC_UNKNOWN_LINUX_GNU_LINKER=riscv64-linux-gnu-gcc \
+    CARGO_TARGET_RISCV64GC_UNKNOWN_LINUX_GNU_RUNNER="qemu-riscv64 -L /usr/riscv64-linux-gnu" \
+    OBJDUMP=riscv64-linux-gnu-objdump

ci/run.sh

@@ -44,6 +44,11 @@ case ${TARGET} in
         export RUSTFLAGS="${RUSTFLAGS} -Ctarget-feature=+neon"
         export TARGET_CFLAGS="-mfpu=vfpv3-d16"
         ;;
+    # Some of our test dependencies use the deprecated `gcc` crates which
+    # doesn't detect RISC-V compilers automatically, so do it manually here.
+    riscv64*)
+        export TARGET_CC="riscv64-linux-gnu-gcc"
+        ;;
 esac
 
 echo "RUSTFLAGS=${RUSTFLAGS}"