ci: build musl only for arm64 and reuse toolchain cache [CI]

packaging/openwrt/install.sh

@@ -84,7 +84,7 @@ load_config() {
     . "$CONF"
     case "$CHANNEL" in release|dev) ;; *) die "invalid channel" ;; esac
     case "$POLICY" in auto|manual) ;; *) die "invalid policy" ;; esac
-    case "$RID" in linux-musl-arm64|linux-musl-x64) ;; *) die "unsupported architecture" ;; esac
+    case "$RID" in linux-musl-arm64) ;; *) die "unsupported architecture" ;; esac
     case "$FEED" in https://*) ;; *) die "feed must use HTTPS" ;; esac
     case "$FEED" in *[!A-Za-z0-9:/._-]*) die "invalid feed URL" ;; esac
     case "$INTERVAL" in ''|*[!0-9]*) die "invalid interval" ;; esac
@@ -270,7 +270,7 @@ install() {
         load_config
         restoring=true
     fi
-    case "$(uname -m)" in aarch64|arm64) detected_rid=linux-musl-arm64 ;; x86_64) detected_rid=linux-musl-x64 ;; *) die "only ARM64 and x86_64 are supported" ;; esac
+    case "$(uname -m)" in aarch64|arm64) detected_rid=linux-musl-arm64 ;; *) die "only ARM64 is supported" ;; esac
     if [ "$restoring" = true ]; then
         [ "$RID" = "$detected_rid" ] || die "saved updater configuration belongs to a different architecture"
     fi