[Nix-dev] a lot of staging changes from me, shout if I broke something! :)

[Gergely Risko]

Hello,

I've pushed some stdenv changes to staging.

The recent merge conflicts broke the stdenv dependency chain on Linux in
the sense that we kept dependencies to bootstrapTools and we also had
multiple zlibs.

These should be fixed now and in efcb00d I also pushed a safe guard for
the future (needs nix 1.8 from the future to actually guard us).

There was also a breakage in staging related to making builds more pure
by passing -D__DATE__=fixvalue (and the same with TIME) in gcc-wrapper
to gcc in an incorrect way (string not quoted).  Hopefully my fix in
e766f0b is the good way to handle this.  The breaking derivation was unzip.

In staging perl tests were re-enabled again by a faulty cherry-pick
merge conflict, I fixed that in 3a2134d.

The commit c5df246 is especially risky to Perl on other platforms than
Linux, so please look out.

I also pushed another refactoring that have been waiting in queue to be
done after the staging -> master merge.

If anything breaks and you need my help to handle it or want to have a
discussion, there are multiple ways to bring my attention quickly:
  - add @errge on github to a discussion,
  - email me personally on gergely at risko.hu,
  - chat me on gergely at risko.hu from GMail.

Of course, I tried to prepare the patches as well as I could, so
hopefully nothing breaks.  These are already committed to staging.

I also have in queue a fix for:
  - having a glibc on Linux that is built by GCC 4.8, not by
    bootstrap-tools (GCC 4.5),
  - having a glibc that actually includes libgcc_s.so, making
    pthread_cancel work without package specific hacks.

These are not committed to staging, I'll propose them as a PR for review
once we know that nothing is broken so far by the previous changes.

Thanks,
Gergely