The script assumed that `wget` was available in the environment
along with common CA certificates.
Replaced the detection of GPG, which is not necessary anymore.
Added pulling the public key bash releases and patches are signed with,
without which we cannot verify signatures.
This comes from:
svn diff ^/nixpkgs/trunk/@18255 ^/nixpkgs/branches/stdenv-updates/ > diff
patch -p0 < diff
and then adding into svn all files new from the patch.
trunk@18255 comes from the last time I updated stdenv-updates from trunk.
svn path=/nixpkgs/stdenv-updates2/; revision=18272
