fix: invoke the USM installer with bash, not sh (busybox ash on alpine can't parse it)

src/cli/Deploy.vala

@@ -732,7 +732,7 @@ private string deploy_containerfile(string base_image, string installer_url, boo
     builder.append("# Install USM. The installer is downloaded to a real file first because it\n");
     builder.append("# extracts its payload relative to $0, so `curl ... | sh` cannot work.\n");
     builder.append("RUN curl -fsSL \"${USM_INSTALLER_URL}\" -o /tmp/install-usm.sh \\\n");
-    builder.append(" && sh /tmp/install-usm.sh -y \\\n");
+    builder.append(" && bash /tmp/install-usm.sh -y \\\n");
     builder.append(" && rm -f /tmp/install-usm.sh\n\n");
     builder.append("COPY usm.config /etc/usm/usm.config\n\n");
     builder.append("COPY repos/ /etc/usm/repos.d/\n");