Fixed buildLocalCabal by defining temporary $HOME

This fixes build error:

building path(s) ‘/nix/store/c8i7gm134aij9330h77l4sdna635yj0a-foo.nix’
building /nix/store/c8i7gm134aij9330h77l4sdna635yj0a-foo.nix
cabal2nix: /homeless-shelter/.cache: createDirectory: does not exist (No such file or directory)
error: syntax error, unexpected $end, at /nix/store/c8i7gm134aij9330h77l4sdna635yj0a-foo.nix:1:1
(use ‘--show-trace’ to show detailed location information)…

(cherry picked from commit 3d8a3e97bdc91c07d3e29c55d4090ab86eb6e38e)
buildLocalCabal: Use host-native nixpkgs for the call to cabal2nix by default

(cherry picked from commit 20113e5d8b45c99d551923e4a0380b5016a62ecd)