pipeline: support riscv64

Currently the Alpine CI jobs are called build-riscv64-emulated, so use
the -emulated suffix also.

mrhlpr/pipeline.py

@@ -14,7 +14,8 @@ def get_arch_alpine_native():
         "x86_64": "x86_64",
         "aarch64": "aarch64",
         "armv6l": "armhf",
-        "armv7l": "armv7"
+        "armv7l": "armv7",
+        "riscv64": "riscv64-emulated",
     }
     if machine in mapping:
         return mapping[machine]