`cabal v2-install xyz` does an `sdist` when run from directory with `.cabal` file

On would think that `cabal v2-install xyz` where `xyz` is a package on hackage only builds and installs `xyz`, but it does other things if the current directory happens to contain a cabal project:
```
$ cabal install happy
Wrote tarball sdist to
/Users/abel/project/open-source/bnfc/dist-newstyle/sdist/BNFC-2.9.2.tar.gz
Resolving dependencies...
Build profile: -w ghc-8.10.5 -O1
In order, the following will be built (use -v for more details):
- happy-1.20.0 (exe:happy) (requires build)
...
$ cabal --version
cabal-install version 3.5.0.0
compiled using version 3.5.0.0 of the Cabal library
```