source $stdenv/setup
mkdir $out
cd $out
tar zxvf $src
# Make the Nix store available to MSYS.
# Hack: we are assuming that the stdenv is based on Cygwin.
nixdir="$(cygpath --windows /nix)"
mkdir $out/nix
cat > $out/etc/fstab <<EOF
#Win32_Path Mount_Point
$nixdir /nix
EOF