buildLocalCabal: allow drvArgs in buildLocalCabalWithArgs

allows to write neat expressions like (as we're still generating an expression
string):

```
{
 build = haskellPackages.buildLocalCabalWithArgs {
   inherit src name;
   drvArgs = {
     jailbreak = false;
     doCheck = false;
   };
 };
}
```

without resorting to weird kung-fu like darcs does:

``` darcs = haskellPackages.darcs.override {
 # A variant of the Darcs derivation that containts only the
 # executable and
 # thus has no dependencies on other Haskell packages.
 cabal = { mkDerivation = x: rec { final = haskellPackages.cabal.mkDerivation
(self: (x final) // {
           isLibrary = false;
           configureFlags = "-f-library"; }); }.final;
         };
};
```

While here, move the `jailbreak = true;` as the default `drvArgs` option.