build-system/haskell: Fix package.conf parsing.

* guix/build/haskell-build-system.scm (register)[conf-depends]: Properly
  react to EOF while reading GHC package conf files.

Merge branch 'master' into core-updates

ruby: Abstract out path to GEM_HOME.

Previously paths to the GEM_HOME of certain Ruby packages were
hard-coded, so packages failed to build when Ruby was updated to 2.3.0.

* guix/build/ruby-build-system.scm (gem-home): New procedure.
* gnu/packages/ruby.scm (ruby-metaclass, ruby-instantiator,
ruby-introspection, ruby-mocha, ruby-minitest-tu-shim): Use it.

build: ruby: Remove cached gem after install.

The .gem file stored in GEM_HOME after install is both redundant and an
archive that stores timestamped files which makes builds
non-deterministic, so delete it after 'gem install'.

* guix/build/ruby-build-system.scm (install): Remove cached gem after
  install.

build: pull: Compile .scm files in one process.

* guix/build/pull.scm (call-with-process, report-build-progress)
(p-for-each): Remove.
(build-guix): Load and compile files in one process.

build-system/gnu: Add 'set-SOURCE-DATE-EPOCH' phase.

This phase is inherited by other build systems, which ensures
'SOURCE_DATE_EPOCH' is always set in practice.

* guix/build/python-build-system.scm (set-SOURCE-DATE-EPOCH): Remove.
(%standard-phases): Don't add it.
* guix/build/gnu-build-system.scm (set-SOURCE-DATE-EPOCH): New
procedure.
(%standard-phases): Add it.
(gnu-build): Remove 'setenv' call for "SOURCE_DATE_EPOCH".

git-download: Correctly implement recursive checkouts.

Previously, the 'git checkout' invocation would remove sub-modules that
had been initialized by 'git clone --recursive'.

* guix/build/git.scm (git-fetch): Never use "git clone --recursive".
Invoke "git submodule update --init --recursive" after "git checkout".
Remove '.git' directories as the last step.

build-system/gnu: Use the long option name for deterministic archives.

This is a followup to 3eb34c6.

* guix/build-system/gnu.scm (gnu-build, gnu-cross-build): Use
"--enable-deterministic-archives" instead of "-D" to work around
Binutils bug <https://sourceware.org/bugzilla/show_bug.cgi?id=17671>.
* guix/build/gnu-build-system.scm (strip): Likewise.

build-system/gnu: Always pass "-D" to strip/objcopy.

* guix/build-system/gnu.scm (gnu-build, gnu-cross-build): Add "-D" to
  #:strip-flags.
* guix/build/gnu-build-system.scm (strip): Likewise.  Also pass "-D" to
  OBJCOPY-COMMAND.

Merge branch 'master' into core-updates

gnu: python: Set SOURCE_DATE_EPOCH to 1 instead of 0.

* gnu/packages/python.scm (python-2)[arguments]: Set SOURCE_DATE_EPOCH
  to 1 to match what the daemon does.
* guix/build/python-build-system.scm (set-SOURCE-DATE-EPOCH): Likewise.

gnu: python-2: Honor 'SOURCE_DATE_EPOCH'.

* gnu/packages/patches/python-2.7-source-date-epoch.patch: New file.
* gnu/packages/python.scm (python-2)[source]: Use it.
  [arguments]: Set SOURCE_DATE_EPOCH in 'patch-lib-shells' phase.
* guix/build/python-build-system.scm (set-SOURCE-DATE-EPOCH): New
  procedure.
  (%standard-phases): Add it.
* gnu-system.am (dist_patch_DATA): Add patch.

graft: Graft files in parallel.

* guix/build/graft.scm (rewrite-directory): Use 'n-par-for-each' instead
  of 'for-each'.

graft: Graft files in a deterministic order.

* guix/build/graft.scm (rewrite-directory)[rewrite-leaf]: Change to take
  a single parameter.  Add call to 'lstat'.  Factorize result of
  'destination'.
  Use 'find-files' instead of 'file-system-fold'.

build-system/gnu: Set 'SOURCE_DATE_EPOCH'.

Suggested by Ludovic Courtès <ludo@gnu.org>.

* guix/build/gnu-build-system.scm (gnu-build): Set SOURCE_DATE_EPOCH for
  deterministic builds.

download: Always use AI_ADDRCONFIG when resolving host names.

* guix/build/download.scm (open-socket-for-uri): Always pass
  AI_ADDRCONFIG to 'getaddrinfo' as recommended in the fine Guile
  manual.
* guix/ftp-client.scm (ftp-open): Ditto.

download: Add timeout parameter for connections.

* guix/build/download.scm (ensure-uri): New procedure.
(current-http-proxy): New variable.
(open-socket-for-uri): Copy from Guile commit aaea5b2, but add #:timeout
parameter and use 'connect*' instead of 'connect'.
(open-connection-for-uri): Add #:timeout parameter and pass it to
'open-socket-for-uri'.

Merge branch 'master' into dbus-update

gnu: ghc: Add GHC_PACKAGE_PATH native search path.

Benefits include: 'guix environment' more useful for ghc libraries, more
useful 'guix package --search-paths' for installed ghc libraries, cleaner
package recipes: no longer need to propagate runtime package dependencies.

* guix/build/haskell-build-system.scm (configure): Unset GHC_PACKAGE_PATH
  around cabal configure.
  (make-ghc-package-database): Use pattern directory search.
  (register): Install complete package database for the current package.
* gnu/packages/haskell.scm (ghc): Add native-search-paths field.

utils: Have search-path-as-list pattern search for directories.

* guix/build/utils.scm (search-path-as-list)[pattern]: Check requested file
  type.  Check pattern against directory names.
* guix/search-paths.scm (evaluate-search-paths)[pattern]: Remove symlink hack.