Fix failing tests

These failures are caused by missing `compiler-project-unit-id`
references.

Author: sgillespie

cabal-testsuite/PackageTests/Path/Compiler/cabal.out

@@ -2,9 +2,11 @@
 compiler-flavour: ghc
 compiler-id: ghc-<GHCVER>
 compiler-path: <GHCPATH>
+compiler-project-unit-id: <ROOT>/cabal.dist/home/.cabal/store/ghc-<GHCVER>
 # cabal path
-{"cabal-version":"<CABAL_INSTALL_VER>","compiler":{"flavour":"ghc","id":"ghc-<GHCVER>","path":"<GHCPATH>"}}
+{"cabal-version":"<CABAL_INSTALL_VER>","compiler":{"flavour":"ghc","id":"ghc-<GHCVER>","path":"<GHCPATH>","project-unit-id":"<ROOT>/cabal.dist/home/.cabal/store/ghc-<GHCVER>"}}
 # cabal path
 compiler-flavour: ghc
 compiler-id: ghc-<GHCVER>
 compiler-path: <GHCPATH>
+compiler-project-unit-id: <ROOT>/cabal.dist/home/.cabal/store/ghc-<GHCVER>