Add dirty and clean install tests

cabal-testsuite/PackageTests/WarnEarlyOverwrite/WarnEarlyOverwrite.cabal

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+cabal-version:      3.0
+name:               WarnEarlyOverwrite
+version:            0.1.0.0
+license:            BSD-3-Clause
+author:             Phil de Joux
+build-type:         Simple
+
+common warnings
+    ghc-options: -Wall
+
+executable warn-early-overwrite
+    import:           warnings
+    main-is:          Main.hs
+    build-depends:    base
+    hs-source-dirs:   app
+    default-language: Haskell2010

cabal-testsuite/PackageTests/WarnEarlyOverwrite/app/Main.hs

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+module Main where
+
+main :: IO ()
+main = putStrLn "Early warning"

cabal-testsuite/PackageTests/WarnEarlyOverwrite/clean-install.out

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+# cabal v2-install
+Wrote tarball sdist to <ROOT>/clean-install.dist/work/./dist/sdist/WarnEarlyOverwrite-0.1.0.0.tar.gz
+Resolving dependencies...
+Build profile: -w ghc-<GHCVER> -O1
+In order, the following will be built:
+ - WarnEarlyOverwrite-0.1.0.0 (exe:warn-early-overwrite) (requires build)
+Configuring executable 'warn-early-overwrite' for WarnEarlyOverwrite-0.1.0.0...
+Preprocessing executable 'warn-early-overwrite' for WarnEarlyOverwrite-0.1.0.0...
+Building executable 'warn-early-overwrite' for WarnEarlyOverwrite-0.1.0.0...
+Installing executable warn-early-overwrite in <PATH>
+Warning: The directory <GBLTMPDIR>/ghc-<GHCVER>/incoming/new-<RAND><GBLTMPDIR>/ghc-<GHCVER>/<PACKAGE>-<HASH>/bin is not in the system search path.
+Symlinking 'warn-early-overwrite' to '<GBLTMPDIR>/warn-early-overwrite'

cabal-testsuite/PackageTests/WarnEarlyOverwrite/clean-install.test.hs

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+import Test.Cabal.Prelude
+
+main = withShorterPathForNewBuildStore $ \storeDir -> cabalTest $ do
+    let options = ["--store-dir=" ++ storeDir, "--installdir=" ++ storeDir]
+    cabalG options "v2-install" []

cabal-testsuite/PackageTests/WarnEarlyOverwrite/dirty-install.out

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+# cabal v2-install
+Wrote tarball sdist to <ROOT>/dirty-install.dist/work/./dist/sdist/WarnEarlyOverwrite-0.1.0.0.tar.gz
+Resolving dependencies...
+Build profile: -w ghc-<GHCVER> -O1
+In order, the following will be built:
+ - WarnEarlyOverwrite-0.1.0.0 (exe:warn-early-overwrite) (requires build)
+Error: [Cabal-7149]
+Path '<GBLTMPDIR>/warn-early-overwrite' already exists. Use --overwrite-policy=always to overwrite.
+# cabal v2-install
+Wrote tarball sdist to <ROOT>/dirty-install.dist/work/./dist/sdist/WarnEarlyOverwrite-0.1.0.0.tar.gz
+Resolving dependencies...
+Build profile: -w ghc-<GHCVER> -O1
+In order, the following will be built:
+ - WarnEarlyOverwrite-0.1.0.0 (exe:warn-early-overwrite) (requires build)
+Configuring executable 'warn-early-overwrite' for WarnEarlyOverwrite-0.1.0.0...
+Preprocessing executable 'warn-early-overwrite' for WarnEarlyOverwrite-0.1.0.0...
+Building executable 'warn-early-overwrite' for WarnEarlyOverwrite-0.1.0.0...
+Installing executable warn-early-overwrite in <PATH>
+Warning: The directory <GBLTMPDIR>/ghc-<GHCVER>/incoming/new-<RAND><GBLTMPDIR>/ghc-<GHCVER>/<PACKAGE>-<HASH>/bin is not in the system search path.
+Symlinking 'warn-early-overwrite' to '<GBLTMPDIR>/warn-early-overwrite'

cabal-testsuite/PackageTests/WarnEarlyOverwrite/dirty-install.test.hs

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+import Test.Cabal.Prelude
+
+import System.FilePath
+
+main = withShorterPathForNewBuildStore $ \storeDir -> cabalTest $ do
+    let options = ["--store-dir=" ++ storeDir, "--installdir=" ++ storeDir]
+    -- Touch the target to see if the warning is made early before the build.
+    _ <- runM "touch" [storeDir </> "warn-early-overwrite"] Nothing
+    fails $ cabalG options "v2-install" []
+    cabalG options "v2-install" ["--overwrite-policy=always"]