Fixes https://github.com/NixOS/nixpkgs/issues/9504.

Note that this means we may have a non-functional /bin/sh in the
chroot while rebuilding Bash or one of its dependencies. Ideally those
packages don't rely on /bin/sh though.

Fixes https://github.com/NixOS/nixos-homepage/issues/46.

Fixes #616.

Fixes #609.

Remove unneeded HAVE_UNSHARE.

* src/libstore/build.cc (CHROOT_ENABLED): Remove HAVE_UNSHARE.

* If the path ends with a slash, drop it.
* If the remaining path doesn’t contain slashes, just return it.

Fixes #574.

This breaks the build on 32-bit systems.

http://hydra.nixos.org/build/24373658

Turns out that "nix-build -vvv" with chroots enabled has been broken
for some time, because some debug message got interpreted as an error.

This can be used to implement functions like ‘imap’ (or for that
matter, ‘map’) without the quadratic complexity incurred by calling
‘++’ repeatedly.

This is a generalisation of replaceChars in Nixpkgs.

This fixes the quadratic behaviour of concatStrings/concatStringsSep
in Nixpkgs.

This reduces the number of Bindings allocations by about 10%.

Pointed out by @cstrahan, thanks!

Conflicts:
	src/libexpr/eval.cc

The value pointers of lists with 1 or 2 elements are now stored in the
list value itself. In particular, this makes the "concatMap (x: if
cond then [(f x)] else [])" idiom cheaper.

These are used thousands of times during NixOS evaluation, so it's
useful to speed them up.

Such as whether Nix is built with signed binary cache support, and the
location of the configuration file.

Turns out getgrouplist() is not POSIX.

http://hydra.nixos.org/build/23881243

This ensures that 1) the derivation doesn't change when Nix changes;
2) the derivation closure doesn't contain Nix and its dependencies; 3)
we don't have to rely on ugly chroot hacks.

In particular, hydra-queue-runner can now distinguish between remote
build / substitution / already-valid. For instance, if a path already
existed on the remote side, we don't want to store a log file.

And make exportPath() less spammy by default.

This is mostly useful for hydra-queue-runner.