For some reason, the bash shell started by 'nix develop' sometimes
reads from stdin, which can hang.

In cross, CXX will look like aarch64-unknown-linux-gnu-g++. We could
run some command to check what kind of compiler it is, but for now we
can just check if g++ is anywhere in the string. I couldn’t find any
"ends with" for makefile, so it can be anywhere in CXX.

Fix a socket length failure on the OSX builders

Reuse the pre-existing list rather than the one written as part of #3777

Cause the time needed to run the testsuite to drop from ~4mins to ~40s

This combines the *.o into a big .o producing one translation unit.
This preserve our unused static initializers, as specified in the C++
standard:

  If no variable or function is odr-used from a given translation
  unit, the non-local variables defined in that translation unit may
  never be initialized (this models the behavior of an on-demand
  dynamic library).

Note that this is very similar to how the --whole-archive flag works.
One advantage of this is that users of the final .a library don’t have
to worry about specifying --whole-archive, or that we have unused
static initializers at all!

(cherry picked from commit 2c692a3b)

The make-rules repo is not maintained.

It's now regenerated when util.hh changes, and is ordered after
config.h to fix a race.

This cuts 'make install -j6' on my laptop from 170s to 134s.

autotools-based systems usually allow user to
append own LDFLAGS like
    LDFLAGS="-Wl,-O1 -Wl,--as-needed -Wl,--hash-style=gnu"
at ./configure stage

This change plumbs LDFLAGS through similar to existing CXXFLAGS variable.

Signed-off-by: Sergei Trofimovich <siarheit@google.com>

This tells Nix to not build the shared libraries.

All plugins in plugin-files will be dlopened, allowing them to
statically construct instances of the various Register* types Nix
supports.

In this mode, the following restrictions apply:

* The builtins currentTime, currentSystem and storePath throw an
  error.

* $NIX_PATH and -I are ignored.

* fetchGit and fetchMercurial require a revision hash.

* fetchurl and fetchTarball require a sha256 attribute.

* No file system access is allowed outside of the paths returned by
  fetch{Git,Mercurial,url,Tarball}. Thus 'nix build -f ./foo.nix' is
  not allowed.

Thus, the evaluation result is completely reproducible from the
command line arguments. E.g.

  nix build --pure-eval '(
    let
      nix = fetchGit { url = https://github.com/NixOS/nixpkgs.git; rev = "9c927de4b179a6dd210dd88d34bda8af4b575680"; };
      nixpkgs = fetchGit { url = https://github.com/NixOS/nixpkgs.git; ref = "release-17.09"; rev = "66b4de79e3841530e6d9c6baf98702aa1f7124e4"; };
    in (import (nix + "/release.nix") { inherit nix nixpkgs; }).build.x86_64-linux
  )'

The goal is to enable completely reproducible and traceable
evaluation. For example, a NixOS configuration could be fully
described by a single Git commit hash. 'nixos-rebuild' would do
something like

  nix build --pure-eval '(
    (import (fetchGit { url = file:///my-nixos-config; rev = "..."; })).system
  ')

where the Git repository /my-nixos-config would use further fetchGit
calls or Git externals to fetch Nixpkgs and whatever other
dependencies it has. Either way, the commit hash would uniquely
identify the NixOS configuration and allow it to reproduced.

Also, don't depend on tput (ncurses). It's really not needed since
ANSI escape sequences have been standardized for 35 years or so.

This fixed the build on ubuntu/debian, where dash is the sh.

I got sick of trying to find the failures in the sea of debug output, so
we now:
- Hide test output unless it fails
- Sprinkle in some simple color
- Pad results for a more tabular look

If Nix is getting a more friendly user interface, we might as well get
a friendlier developer interface, right? :)

this is needed for pipe2()

This reverts commit f78126bf. There
really is no need for such a massive change...

Eventually the nested if statements should be replaced by a more general
condition, but this is sufficient to make it work on FreeBSD.

1. Shared lib extension is .dll
2. Shared libs are installed to $(prefix)/bin
3. Linker does not support -z flag

3.81 doesn't understand the ‘define foo =’ syntax, which was added in
3.82.  So use ‘define foo’ instead.

This makes it easier to use with "git subtree".

Source: http://blog.jgc.org/2011/07/gnu-make-recursive-wildcard-function.html