docker build fail

[aamehedi]

OS: Arch Linux

❯ docker --version
Docker version 20.10.10, build b485636f4b

❯ git log | head -n1
commit 20899bb3bebc51e06e7c431167fd48c6f7b11e73

Successfully tagged 127.0.0.1:5000/rubydoc-app:latest
Sending build context to Docker daemon     697B
Step 1/10 : FROM ruby:3-alpine3.13
 ---> de0a201a0a49
Step 2/10 : ADD ./generate.rb /rb/generate.rb
 ---> 01344bda743d
Step 3/10 : RUN chmod +x /rb/generate.rb
 ---> Running in e7249974945e
 ---> 7c43697d0a25
Step 4/10 : RUN adduser -D app
 ---> Running in 323aad87f1b5
 ---> d2116efa7fc5
Step 5/10 : USER app
 ---> Running in 78e8bcad2986
 ---> 2973f3b9dc58
Step 6/10 : ENV GEM_HOME /home/app/.gems
 ---> Running in 654768d55f43
 ---> 6143583a84b1
Step 7/10 : RUN gem update --system --no-document
 ---> Running in 661ce68e1f2b
Updating rubygems-update
Successfully installed rubygems-update-3.2.31
Installing RubyGems 3.2.31
ERROR:  While executing gem ... (Errno::EACCES)
    Permission denied @ dir_s_mkdir - /usr/local/lib/ruby/site_ruby/3.0.0/rubygems
 ---> b9e1f66b5ef3
Step 8/10 : RUN gem install --no-document bundler yard
 ---> Running in dd6bca00796a
Successfully installed bundler-2.2.31
Successfully installed yard-0.9.26
2 gems installed
 ---> 77e144798897
Step 9/10 : WORKDIR /build
 ---> Running in 86e6cdb47607
 ---> 6e98e0f2a7ec
Step 10/10 : ENTRYPOINT ["/rb/generate.rb"]
 ---> Running in 9b317efbaf10
 ---> 0e86847213e8
Successfully built 0e86847213e8