Unable to run build, mkdir permission denied

[benc-uk]

Running make build-run results in an error on line 11 of the Dockerfile (where jekyll build is run), adding --trace gives more details, which is a permission error on the mkdir step

This is using Docker running inside WSL2

docker build -t azch/aks-site:latest -f Dockerfile .
Sending build context to Docker daemon  49.91MB
Step 1/8 : FROM jekyll/builder AS build
 ---> 40cf7a7e8f7e
Step 2/8 : WORKDIR /src/app
 ---> Using cache
 ---> 67ac0a23d069
Step 3/8 : COPY . .
 ---> Using cache
 ---> f920d20498cb
Step 4/8 : RUN mkdir _site &&     jekyll build --future --trace
 ---> Running in 4a8b5106a410
ruby 2.6.4p104 (2019-08-28 revision 67798) [x86_64-linux-musl]
Configuration file: /src/app/_config.yml
/usr/local/lib/ruby/2.6.0/fileutils.rb:239:in `mkdir': Permission denied @ dir_s_mkdir - /src/app/.jekyll-cache (Errno::EACCES)
        from /usr/local/lib/ruby/2.6.0/fileutils.rb:239:in `fu_mkdir'
        from /usr/local/lib/ruby/2.6.0/fileutils.rb:217:in `block (2 levels) in mkdir_p'
        from /usr/local/lib/ruby/2.6.0/fileutils.rb:215:in `reverse_each'
        from /usr/local/lib/ruby/2.6.0/fileutils.rb:215:in `block in mkdir_p'
        from /usr/local/lib/ruby/2.6.0/fileutils.rb:200:in `each'
        from /usr/local/lib/ruby/2.6.0/fileutils.rb:200:in `mkdir_p'
        from /usr/gem/gems/jekyll-4.0.0/lib/jekyll/cache.rb:184:in `dump'
        from /usr/gem/gems/jekyll-4.0.0/lib/jekyll/cache.rb:101:in `[]='
        from /usr/gem/gems/jekyll-4.0.0/lib/jekyll/cache.rb:45:in `clear_if_config_changed'
        from /usr/gem/gems/jekyll-4.0.0/lib/jekyll/site.rb:113:in `reset'
        from /usr/gem/gems/jekyll-4.0.0/lib/jekyll/site.rb:33:in `initialize'
        from /usr/gem/gems/jekyll-4.0.0/lib/jekyll/commands/build.rb:30:in `new'
        from /usr/gem/gems/jekyll-4.0.0/lib/jekyll/commands/build.rb:30:in `process'
        from /usr/gem/gems/jekyll-4.0.0/lib/jekyll/command.rb:89:in `block in process_with_graceful_fail'
        from /usr/gem/gems/jekyll-4.0.0/lib/jekyll/command.rb:89:in `each'
        from /usr/gem/gems/jekyll-4.0.0/lib/jekyll/command.rb:89:in `process_with_graceful_fail'
        from /usr/gem/gems/jekyll-4.0.0/lib/jekyll/commands/build.rb:18:in `block (2 levels) in init_with_program'
        from /usr/gem/gems/mercenary-0.3.6/lib/mercenary/command.rb:220:in `block in execute'
        from /usr/gem/gems/mercenary-0.3.6/lib/mercenary/command.rb:220:in `each'
        from /usr/gem/gems/mercenary-0.3.6/lib/mercenary/command.rb:220:in `execute'
        from /usr/gem/gems/mercenary-0.3.6/lib/mercenary/program.rb:42:in `go'
        from /usr/gem/gems/mercenary-0.3.6/lib/mercenary.rb:19:in `program'
        from /usr/gem/gems/jekyll-4.0.0/exe/jekyll:15:in `<top (required)>'
        from /usr/gem/bin/jekyll:23:in `load'
        from /usr/gem/bin/jekyll:23:in `<main>'
The command '/bin/sh -c mkdir _site &&     jekyll build --future --trace' returned a non-zero code: 1
Makefile:17: recipe for target 'build-run' failed
make: *** [build-run] Error 1

[benc-uk]

As per this GH issue jekyll/jekyll#7591 (comment)
Fixed by adding an empty .jekyll-cache directory as described above

RUN mkdir _site && mkdir .jekyll-cache && \
    jekyll build --future

[sabbour]

Do you mind submitting a PR for this? :)

[benc-uk]

Will do!
I've got an PR incoming with this, but also a bunch of things we've discovered trying to run through without clicking "toggle solution"

[sabbour]

Fixed.