MULTIARCH-3441: Enable builds for s390x (#1) (#2)

- Update the .goreleaser.yaml to include s390x
- Update the cross build for s390x
- Link gcc to s390x-linux-gnu-gcc binary

On s390x go compiler seems to expect the gcc binary at
s390x-linux-gnu-gcc binary. However on rhel it is not installed there.

Signed-off-by: Jan Schintag <jan.schintag@de.ibm.com>

Dockerfile

@@ -32,6 +32,13 @@ RUN set -ex \
      && ln -f /usr/local/go/bin/go /usr/bin/go                                  \
      && ln /usr/bin/gcc /usr/bin/s390x-linux-gnu-gcc
 
+#################################################################################
+# Link gcc to /usr/bin/s390x-linux-gnu-gcc as go requires it on s390x
+RUN ARCH=$(arch | sed 's|x86_64|amd64|g')                                       \
+     && [ "${ARCH}" == "s390x" ]                                                \
+     && ln /usr/bin/gcc /usr/bin/s390x-linux-gnu-gcc                            \
+     || echo "Not running on s390x, skip linking gcc binary"
+
 WORKDIR /build
 ENTRYPOINT ["make"]
 CMD []