Specify target specific linker for riscv64gc-gnu job

Author: Hoverbear

src/ci/docker/host-x86_64/disabled/riscv64gc-gnu/Dockerfile

@@ -91,7 +91,9 @@ RUN sh /scripts/sccache.sh
 # Avoid "fatal: detected dubious ownership in repository at '/checkout'" error
 RUN git config --global --add safe.directory /checkout
 
-ENV RUST_CONFIGURE_ARGS --qemu-riscv64-rootfs=/tmp/rootfs
+ENV RUST_CONFIGURE_ARGS \
+    --qemu-riscv64-rootfs=/tmp/rootfs \
+    --set target.riscv64gc-unknown-linux-gnu.linker=riscv64-linux-gnu-gcc
 ENV SCRIPT python3 ../x.py --stage 2 test --host='' --target riscv64gc-unknown-linux-gnu
 
 ENV NO_CHANGE_USER=1