forgejo/workflows: add a native loongarch64 runner to the fate matrix

The linux-loongarch64 entry runs the same fate job on native LoongArch64
hardware (Loongson-3C5000, 64 cores) instead of emulating it with qemu.
Like the other entries it needs no container: the runner label carries the
image, and jobs run unprivileged inside a rootless docker daemon.

Signed-off-by: jinbo <jinbo@loongson.cn>

.forgejo/workflows/test.yml

@@ -25,6 +25,9 @@ jobs:
           - runner: linux-amd64
             shared: 'shared'
             bits: '64'
+          - runner: linux-loongarch64
+            shared: 'static'
+            bits: '64'
     runs-on: ${{ matrix.runner }}
     steps:
       - name: Checkout