Run tests nightly on riscv64 runner

Reviewed-by: Saša Nedvědický <sashan@openssl.org>
Reviewed-by: Paul Dale <ppzgs1@gmail.com>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/27240)

.github/workflows/os-zoo.yml

diff --git a/.github/workflows/os-zoo.yml b/.github/workflows/os-zoo.yml
index 00a9228..b58e977 100644
--- a/.github/workflows/os-zoo.yml
+++ b/.github/workflows/os-zoo.yml
@@ -211,6 +211,23 @@
     - name: make test
       run: make test HARNESS_JOBS=${HARNESS_JOBS:-4}
 
+  linux-riscv64:
+    runs-on: linux-riscv64
+    steps:
+    - uses: actions/checkout@v4
+    - name: config
+      run: ./config enable-fips enable-ec_nistp_64_gcc_128 enable-md2 enable-rc5 enable-ssl3 enable-ssl3-method enable-trace
+    - name: config dump
+      run: ./configdata.pm --dump
+    - name: make
+      run: make -j8
+    - name: get cpu info
+      run: ./util/opensslwrap.sh version -c
+    - name: make test
+      env:
+        OPENSSL_riscvcap: ZBA_ZBB_ZBC_ZBS_ZKT
+      run: make test HARNESS_JOBS=${HARNESS_JOBS:-4}
+
   freebsd-x86_64:
     runs-on: ubuntu-latest
     steps: