Add symbolic link for yarnpkg (#7894)

Dockerfile

@@ -52,6 +52,7 @@ RUN apk -U upgrade \
  && rm yarn.tar.gz \
  && mv /tmp/src/yarn-v$YARN_VERSION /opt/yarn \
  && ln -s /opt/yarn/bin/yarn /usr/local/bin/yarn \
+ && ln -s /opt/yarn/bin/yarnpkg /usr/local/bin/yarnpkg \
  && wget -O libiconv.tar.gz "https://ftp.gnu.org/pub/gnu/libiconv/libiconv-$LIBICONV_VERSION.tar.gz" \
  && echo "$LIBICONV_DOWNLOAD_SHA256 *libiconv.tar.gz" | sha256sum -c - \
  && tar -xzf libiconv.tar.gz -C /tmp/src \

bin/yarn

@@ -2,7 +2,7 @@
 APP_ROOT = File.expand_path('..', __dir__)
 Dir.chdir(APP_ROOT) do
   begin
-    exec "yarnpkg #{ARGV.join(' ')}" unless Dir.exist?('node_modules')
+    exec "yarnpkg", *ARGV
   rescue Errno::ENOENT
     $stderr.puts "Yarn executable was not detected in the system."
     $stderr.puts "Download Yarn at https://yarnpkg.com/en/docs/install"