Edit Datafiles test to check cabal projects too

cabal-testsuite/PackageTests/NewBuild/CmdRun/Datafiles/cabal.out

@@ -2,7 +2,7 @@
 Resolving dependencies...
 Build profile: -w ghc-<GHCVER> -O1
 In order, the following will be built:
- - Datafiles-1.0 (exe:foo) (first run)
-Configuring executable 'foo' for Datafiles-1.0..
-Preprocessing executable 'foo' for Datafiles-1.0..
-Building executable 'foo' for Datafiles-1.0..
+ - foo-1.0 (exe:foo) (first run)
+Configuring executable 'foo' for foo-1.0..
+Preprocessing executable 'foo' for foo-1.0..
+Building executable 'foo' for foo-1.0..

cabal-testsuite/PackageTests/NewBuild/CmdRun/Datafiles/cabal.project

-packages: .
+packages: foo

cabal-testsuite/PackageTests/NewBuild/CmdRun/Datafiles/Main.hs → cabal-testsuite/PackageTests/NewBuild/CmdRun/Datafiles/foo/Main.hs

-import Paths_Datafiles
+import Paths_foo
 
 main = putStrLn =<< readFile =<< getDataFileName "hello.txt"
 

cabal-testsuite/PackageTests/NewBuild/CmdRun/Datafiles/Datafiles.cabal → cabal-testsuite/PackageTests/NewBuild/CmdRun/Datafiles/foo/foo.cabal

-name: Datafiles
+name: foo
 version: 1.0
 build-type: Simple
 cabal-version: >= 1.10