Add basic test for new-exec

cabal-testsuite/PackageTests/NewBuild/CmdExec/GhcInvocation/Main.hs

+import InplaceDep
+main = f

cabal-testsuite/PackageTests/NewBuild/CmdExec/GhcInvocation/cabal.out

+# cabal new-build
+Resolving dependencies...
+Build profile: -w ghc-<GHCVER> -O1
+In order, the following will be built:
+ - inplace-dep-1.0 (lib) (first run)
+Configuring library for inplace-dep-1.0..
+Preprocessing library for inplace-dep-1.0..
+Building library for inplace-dep-1.0..
+# cabal new-exec

cabal-testsuite/PackageTests/NewBuild/CmdExec/GhcInvocation/cabal.project

+packages:
+  inplace-dep

cabal-testsuite/PackageTests/NewBuild/CmdExec/GhcInvocation/cabal.test.hs

+import Test.Cabal.Prelude
+import Control.Monad.Trans (liftIO)
+import System.Directory-- (getDirectoryContents, removeFile)
+main = cabalTest $ do
+    cabal "new-build" ["inplace-dep"]
+    env <- getTestEnv
+    liftIO $ removeEnvFiles $ testSourceDir env -- we don't want existing env files to interfere
+    cabal "new-exec" ["ghc", "Main.hs"]
+    -- TODO external (store) deps, once new-install is working
+
+removeEnvFiles :: FilePath -> IO ()
+removeEnvFiles dir = (mapM_ (removeFile . (dir </>))
+                   . filter
+                       ((".ghc.environment" ==)
+                       . take 16))
+                   =<< getDirectoryContents dir
+

cabal-testsuite/PackageTests/NewBuild/CmdExec/GhcInvocation/inplace-dep/InplaceDep.hs

+module InplaceDep ( f ) where
+
+f :: IO ()
+f = putStrLn "Hello world"
+

cabal-testsuite/PackageTests/NewBuild/CmdExec/GhcInvocation/inplace-dep/inplace-dep.cabal

+name: inplace-dep
+version: 1.0
+build-type: Simple
+cabal-version: >= 1.10
+
+library
+    exposed-modules: InplaceDep
+    build-depends: base
+    default-language: Haskell2010
+