Create noindex.cache if missing

[jasagredo]

Fixes #9891 by creating the file if it is missing.

Depends on #10728

QA

This will work on Linux:

cabal init -m -n --simple --lib
mkdir repo
echo "packages: ." > cabal.project
echo "repository local" >> cabal.project
echo "  url: file+noindex://$(pwd)/repo" >> cabal.project
cabal build

For Windows, the path has to be un-cygwinize and prepended by //./ as described in #10728.

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