rabbitmq-server: Fix building on Darwin

On Darwin, settin HOME=/build before calling rabbitmqctl doesn't work:
it produces an error while trying to create a file in /build because the
/build directory doesn't exist. It also doesn't work when building using
"nix develop". So, we set HOME=$TMPDIR instead which does work in those
cases.

pkgs/by-name/ra/rabbitmq-server/package.nix

@@ -112,7 +112,7 @@ stdenv.mkDerivation rec {
   doInstallCheck = true;
   installCheckPhase = ''
     runHook preInstallCheck
-    out="$(env - LANG=C.utf8 HOME=/build ${placeholder "out"}/bin/rabbitmqctl version)"
+    out="$(env - LANG=C.utf8 HOME=$TMPDIR ${placeholder "out"}/bin/rabbitmqctl version)"
     if [[ "$out" != "$version" ]]; then
       echo "Rabbitmq should report version $version, but thinks it's version $out" >&2
       exit 1