fix: install libgirepository1.0-dev to make gobject-introspection:4.2…

….2 gem install

It's a dependency of cairo, and it fails to install the package by itself during bundle install.
It seems that it clashes with some other gem during parallel installation. The alternative and probably
less fragile solution would be to set number of bundler jobs to 1, but I figured that it's
not worth compromising performance when such a simple workaround exists

Exact error:
"apt-get install -V -y libgirepository1.0-dev"
E: Could not get lock /var/lib/dpkg/lock-frontend. It is held by process 823 (apt-get)
E: Unable to acquire the dpkg frontend lock (/var/lib/dpkg/lock-frontend), is another process using it?
installing 'libgirepository1.0-dev' native package... failed
Failed to run 'apt-get install -V -y libgirepository1.0-dev'

Dockerfile

@@ -9,6 +9,8 @@ RUN apt-get update && apt-get install -yyq --no-install-recommends \
   libgdk-pixbuf2.0-dev \
   imagemagick \
   liblcms2-utils \
+  # When girepository tries to install implicitly, there's an error due to apt being locked; details in commit message
+  libgirepository1.0-dev \
   && apt-get clean \
   && rm -rf /va/lib/apt/lists/*