Add (guix build union).

* guix/build/union.scm, tests/union.scm: New files.
* Makefile.am (MODULES): Add `guix/build/union.scm'.
  (TESTS): Add `tests/union.scm'.

release.nix: Change `distro.hello' to produce something.

* release.nix (distro.hello)[buildPhase]: Tee the log to $out.  Add a
  `name' attribute; remove `buildInputs' and instead use the full path
  to `guix-build'.

distro: Build Bash sequentially.

* distro/packages/base.scm (bash): Set `#:parallel-build?' and
  `#:parallel-tests?' to #f.

tests: Use our own bootstrap tools.

* tests/builders.scm (%bootstrap-inputs): Use %BOOT0-INPUTS from the distro.
* tests/packages.scm (%bootstrap-inputs): Likewise.
* tests/derivations.scm (%coreutils): Alias for %BOOTSTRAP-COREUTILS&CO.

release.nix: Add a `distro.hello' job.

* release.nix (distro.hello): New job.

build: Preserve the executable bit of bootstrap binaries.

* Makefile.am (install-data-hook): New target.

build: Make sure scripts know where to find their modules.

* guix-build.in, guix-download.in: Define `prefix' and `datarootdir', so
  that `guilemoduledir' expands to something meaningful.

release.nix: Pre-download the Guile bootstrap tarball.

* release.nix (bootstrap_guile): New variable.
  (build)[preBuild]: New attribute.

build: Fix out-of-source-tree builds.

* Makefile.am (distro/packages/bootstrap/x86_64-linux/guile-bootstrap-2.0.6.tar.xz,
  distro/packages/bootstrap/i686-linux/guile-bootstrap-2.0.6.tar.xz):
  Make the target's parent directory.
* pre-inst-env.in (DISTRO_BOOTSTRAP_PATH): Add the builddir-relative
  directory.

distro: Change $DISTRO_{PATCH,BOOTSTRAP}_DIRECTORY to search paths.

* distro.scm (not-colon): New variable.
  (%patch-directory): Rename to...
  (%patch-path): ... this.  Turn into a list.  Expect $DISTRO_PATCH_PATH
  to be a colon-separated search path.
  (%bootstrap-binaries-directory): Rename to...
  (%bootstrap-binaries-path): ... this.  Likewise.
  (search-patch, search-bootstrap-binary): Adjust accordingly.

* pre-inst-env.in: Change to use `DISTRO_PATCH_PATH' and
  `DISTRO_BOOTSTRAP_PATH'.

release.nix: Set succeed-on-failure and build-out-source-tree.

* release.nix: Define `succeedOnFailure', `keepBuildDirectory', and
  `buildOutOfSourceTree'.
  (build): Inherit them.

build: Move `distro/patches' to `distro/packages/patches'.

* distro/patches: Move directory to...
* distro/packages/patches: ... here.
* Makefile.am (dist_patch_DATA): Adjust accordingly.
* pre-inst-env.in (DISTRO_PATCH_DIRECTORY): Likewise.

build: Use `pre-inst-env' to compile the source.

* Makefile.am (.scm.go): Use `pre-inst-env' instead of re-defining the
  environment variables, except for `DISTRO_INSTALLED_PATCH_DIRECTORY'
  and `DISTRO_INSTALLED_BOOTSTRAP_DIRECTORY'.

guix-build: Gracefully handle `&package-input-error' conditions.

* guix/packages.scm: Export `package-error?' and `package-input-error?'.
* guix-build.in (guix-build): Catch `&package-input-error' conditions,
  print a human-readable message, and exit.

location: Start column numbers at 1.

* guix/utils.scm (source-properties->location): Use COL + 1.

distro: Add i686-linux port.

* distro/packages/bootstrap/i686-linux/bash,
  distro/packages/bootstrap/i686-linux/mkdir,
  distro/packages/bootstrap/i686-linux/tar,
  distro/packages/bootstrap/i686-linux/xz: New files.

* distro/packages/base.scm (%bootstrap-coreutils&co,
  %bootstrap-binutils, %bootstrap-glibc, %bootstrap-gcc): Add hashes of
  the i686-linux tarballs.

* Makefile.am (bootstrap_i686_linuxdir, dist_bootstrap_i686_linux_DATA,
  nodist_bootstrap_i686_linux_DATA): New variables
  (DISTCLEANFILES): Add $(nodist_bootstrap_i686_linux_DATA).
  (distro/packages/bootstrap/i686-linux/guile-bootstrap-2.0.6.tar.xz):
  New rule.

distro: gcc: Adjust to support non-x86_64 architectures.

* distro/packages/base.scm (gcc-4.7)[arguments]: In the `pre-configure'
  phase, patch all the relevant gcc/config files, not just those for
  x86_64-linux-gnu.

utils: Remove special `substitute*' syntax for lists of files.

* guix/build/utils.scm (substitute*): Remove special syntax for
  list-of-files; instead, check whether FILE is `list?' at run time.

* distro/packages/base.scm (gcc-4.7, %binutils-static): Adjust
  accordingly.

doc: Add `HACKING'.

* HACKING: New file.
* Makefile.am (EXTRA_DIST): Add it.

Add a `system' parameter to `nixpkgs-derivation'.

* guix/utils.scm (nixpkgs-derivation): Add a `system' parameter.  Pass
  it in the `nix-instantiate' invocation.