distro: recutils: Allow builds with glibc 2.16+.

* distro/base.scm (recutils): Apply. `diffutils-gets-undeclared.patch'.

distro: glibc: Propagate Linux headers.

* distro/base.scm (glibc): Move LINUX-HEADERS from `native-inputs' to
  `propagated-inputs'.  Remove unnecessary `_' in /bin/pwd substitution.

distro: diffutils: Allow builds with glibc 2.16+.

* distro/patches/diffutils-gets-undeclared.patch: New file.
* Makefile.am (dist_patch_DATA): Add it.

* distro/base.scm (diffutils): Apply. `diffutils-gets-undeclared.patch'.

distro: tar: Allow builds with glibc 2.16+.

* distro/patches/tar-gets-undeclared.patch: New file.
* Makefile.am (dist_patch_DATA): Add it.

* distro/base.scm (tar): Apply. `tar-gets-undeclared.patch'.

packages: Add a printer for <package>.

* guix/packages.scm (<package>): Add record printer.

Optimize `write-derivation' and `derivation-path->output-path'.

* guix/derivations.scm (write-derivation): Explicitly use
  `simple-format'.
  (derivation-path->output-path): Memoize.

Optimize `store-path?'.

* guix/store.scm (store-path?): Check with `string-prefix?' instead of a
  regexp.

build-system/gnu: Really apply patches.

* guix/build/gnu-build-system.scm (patch): Use `--input FILE', not just
  `FILE'.

utils: Change `substitute*' to allow iteration over several matches.

* guix/build/utils.scm (substitute): Do not pass the OUT to PROC; use
  `list-matches' instead of `regexp-exec' and pass a list of matches to
  PROC. Expect PROC to return a string, and output that.  Fold over
  RX+PROC in order.  Use `(read-line p 'concat)' to include the trailing
  delimiter in LINE.
  (substitute*): Produce code to iterate over the matches, and return a
  string, which includes anything from the original line that's in
  between matches.

* distro/base.scm (gcc-4.7, glibc): Adjust accordingly: remove use
  of (ice-9 regex) and `regexp-substitute/global'; return a string.

distro: m4: Add patch to allow builds with glibc 2.16+.

* distro/base.scm (m4): Use `m4-gets-undeclared.patch'.

* distro/patches/m4-gets-undeclared.patch: New file.
* Makefile.am (dist_patch_DATA): Add it.

Add a `guile-for-build' parameter to `build-expression->derivation'.

* guix/derivations.scm (%guile-for-build): Use `nixpkgs-derivation*'
  instead of `nixpkgs-derivation'.
  (build-expression->derivation): New `guile-for-build' keyword
  parameter.  Use it.

Add an `env-vars' keyword parameter to `build-expression->derivation'.

* guix/derivations.scm (build-expression->derivation): New `env-vars'
  keyword parameter; default to '().  Use it.

build-system/gnu: Add `path-exclusions' parameter.

* guix/build/gnu-build-system.scm (set-paths): Add new `path-exclusions'
  parameter; honor it.
* guix/build-system/gnu.scm (gnu-build): New `path-exclusions' keyword
  parameter; pass it to BUILDER.

* distro/base.scm (gcc-4.7): Exclude "libc" from $LIBRARY_PATH.

distro: gcc: Allow `libstdc++' to be found.

* distro/base.scm (gcc-4.7): Add `-rpath' arguments to `LIB_SPEC' to
  allow `libstdc++' to be found by users.

distro: gcc: Pass #:strip-binaries?.

* distro/base.scm (gcc-4.7): Pass #:strip-binaries?.

build-system/gnu: Honor the `patch-shebangs?' and `strip-binaries?' parameters.

* guix/build/gnu-build-system.scm (patch-shebangs): Honor
  PATCH-SHEBANGS?.
  (strip): Honor STRIP-BINARIES?.  Display a message from `strip-dir'.

guix-build: Fix the "unrecognized option" error message.

* guix-build.in (guix-build): Show the option name when an unrecognized
  option is passed.

build-system/gnu: Add a `strip' phase.

* guix/build/gnu-build-system.scm (strip): New procedure.
  (%standard-phases): Add it.

* guix/build-system/gnu.scm (gnu-build): New `strip-binaries?',
  `strip-flags', and `strip-directories' keyword parameters.  Pass them
  to BUILDER.

build-system/gnu: Always invoke `configure' with a relative path.

* guix/build/gnu-build-system.scm (configure): Change SRCDIR to always
  be a relative path.

distro: gcc: Do not store configure flags in the resulting binaries.

* distro/base.scm (gcc-4.7): Add a `post-configure' phase to clear
  `TOPLEVEL_CONFIGURE_ARGUMENTS' in the top-level `Makefile'.