CI: Fix error when running on host-arm

When pulling a base image from Docker Hub, the architecture defaults to
that of the native host, which is typically x86_64 or amd64 on GitHub
runners. Since the run-on-arch-action GitHub Action aims to run shecc on
an Armv7 Ubuntu image, it attempts to pull the native host manifest
(either x86_64 or amd), resulting in a 'no match for platform in manifest'
error unless the --platform option is specified. Therefore, specifying
the --platform option as linux/arm64 resolves this issue.

.github/workflows/main.yml

@@ -34,10 +34,11 @@ jobs:
     - name: build artifact
       # The GitHub Action for non-x86 CPU
       # https://github.com/uraimo/run-on-arch-action
-      uses: uraimo/run-on-arch-action@v2.7.1
+      uses: uraimo/run-on-arch-action@v2
       with:
-        arch: armv7
-        distro: ubuntu22.04
+        arch: none
+        distro: none
+        base_image: "--platform=linux/armv7 armv7/ubuntu:22.04"
         install: |
           apt-get update -q -y
           apt-get install -q -y build-essential