Cardano Node Installation process: add cabal update

[schmidko]

Checklist

• I have read the How to Contribute.
• I have run yarn build after adding my changes without getting any errors.

Updating documentation or Bugfix

The documentation regarding the installation of the Cardano node could benefit from a minor update. Specifically, there is a crucial step missing: running "cabal update" before executing the "cabal configure --with-compiler=ghc-8.10.7" command. It's easy for users to miss the warning and this leading to confusion when the node build doesn't proceed as expected.

[rphair]

Already added to docs/get-started/installing-cardano-node.md in #1008 but for some reason got missed in this page (it might still have been in the development branch at the time).

@rdlrt @os11k I would normally do cabal update immediately before cabal build but maybe it's better the way it's presented here, e.g. if people are using more than one version of GHC (personally I don't, so haven't investigated). 🤔

[rdlrt]

Already added to docs/get-started/installing-cardano-node.md in #1008 but for some reason got missed in this page (it might still have been in the development branch at the time).

@rdlrt @os11k I would normally do cabal update immediately before cabal build but maybe it's better the way it's presented here, e.g. if people are using more than one version of GHC (personally I don't, so haven't investigated). 🤔

I'd imagine configure will be (more often than not) a once-off...and should always occur prior to cabal update , I'd also go with executing it right before build.