This is a follow-up to a169553f7e.
In most cases it should allow the TLS verification to be enabled.
It also makes the behavior of `fetchurl` more consistent with other fetchers
like `fetchgit`.
Ideally we would always fallback on `cacert` but I am not sure how to build
`cacert` during bootstrap without making an unmaintainable mess.
This make sure the credentials cannot be leaked in a MITM attack.
Note that this change might break some existing deployments if the users
tries to fetch resources on endpoints with invalid certificates.
The impacted users will have the following choices:
* fix the endpoint providing the resource
* override SSL_CERT_FILE to either disable the verification (not
recommended) or to set it to a path including their CA certificate.
When specifying the `builder` attribute in `stdenv.mkDerivation`, this
will be effectively transformed into
builtins.derivation {
builder = stdenv.shell;
args = [ "-e" builder ];
}
This also means that `default-builder.sh` is never sourced and as a
result it's not guaranteed that `$NIX_ATTRS_SH_FILE` is set to a correct
location[1].
Also, we need to source `.attrs.sh` to source `$stdenv`. So, the
following is done now:
* If `$NIX_ATTRS_SH_FILE` points to a correct location, then use it.
Directly using `.attrs.sh` is problematic for `nix-shell(1)` usage
(see previous commit for more context), so prefer the environment
variable if possible.
* Otherwise, if `.attrs.sh` exists, then use it. See [1] for when this
can happen.
* If neither applies, it can be assumed that `__structuredAttrs` is
turned off and thus nothing needs to be done.
[1] It's possible that it doesn't exist at all - in case of Nix 2.3 or
it can point to a wrong location on older Nix versions with a bug in
`__structuredAttrs`.
The kent.dl.sourceforge.net domain doesn't seem to exist anymore. Because it's
not usable, this commit removes it from the list of sourceforge mirrors.
A full check would be more complicated to write -
and more importantly - probably also more expensive.
Motivation: eval-time catch for errors like in commit 8198636be0.
It's impossible to pass arguments with spaces with curlOpts.
curlOptsList supports that. Passing a list to curlOpts has been
deprecated. This commit is fully backwards compatible.
