gnu-build-system: Dump the values of environment variables.

* guix/build/gnu-build-system.scm (set-paths): Dump the value of
  environment variables in the `environment-variables' files, similar to
  what Nixpkgs does.

packages: Allow inputs that are local files.

* guix/packages.scm (package-derivation): Add to the store inputs that
  are local files.

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

* guix/build/gnu-build-system.scm (patch): New procedure.
  (%standard-phases): Add `patch'.

* guix/build-system/gnu.scm (gnu-build): Add `patches' and `patch-flags'
  parameters.  Pass them on.

build-system/gnu: Make the builder's module list a parameter.

* guix/build-system/gnu.scm (gnu-build): Add a `modules' keyword
  parameter; use it.

Add builder-side utilities for phases, stream editing, & co.

* guix/build/utils.scm (with-directory-excursion): New macro.
  (alist-cons-before, alist-cons-after, alist-replace): New procedures.
  (substitute): New procedure.

* tests/build-utils.scm: New file.

* Makefile.am (TESTS): Add `tests/build-utils.scm'.

packages: Add a `self-native-input?' field.

* guix/packages.scm (<package>)[self-native-input?]: New field.
  (package-derivation): Update/fix pattern.

Rename <package-source> to <origin>; use the `letrec*' behavior in packages.

* guix/packages.scm (<package-source>): Rename to...
  (<origin>): ... this.  Update users.

* distro/base.scm (libsigsegv, gawk, hello): Adjust to renaming; refer
  to VERSION to build the URL.

define-record-type*: Add `letrec*' behavior.

* guix/utils.scm (define-record-type*)[make-syntactic-constructor]: Bind
  all the ((FIELD VALUE) ...) in a `letrec*'.  Adjust `field-value'
  accordingly.

* tests/utils.scm ("define-record-type* with letrec* behavior"): New
  test.

Add a `base32' macro, for convenience.

* guix/packages.scm (base32): New macro.

* distro/base.scm (libsigsegv, gawk, hello): Use it.

packages: Allow the `arguments' field to be a procedure.

* guix/packages.scm (package-derivation): When ARGS is a procedure, call
  (ARGS SYSTEM).

* distro/base.scm (gawk)[arguments]: Turn into a procedure, to disable
  tests on Cygwin.

gnu-build-system: Improve the `configure' and `check' phases.

* guix/build/gnu-build-system.scm (configure): Print the final list of
  flags.
  (check): Add `tests?' keyword parameter.

gnu-build-system: Print the `configure' flags.

* guix/build/gnu-build-system.scm (configure): Print CONFIGURE-FLAGS.

Make `define-record-type*' error messages more informative.

* guix/utils.scm (define-record-type*): In case of missing or extra
  field initializers, raise a descriptive `syntax-error'.

distro: libsigsegv: Use multiple outputs.

* distro/base.scm (libsigsegv)[outputs]: New field
  (gawk)[arguments]: Clear.
  [inputs]: Add the "lib" output of LIBSIGSEGV.

guix-build: Display multiple outputs when needed.

* guix-build.in (guix-build): Display multiple outputs when there's more
  than one.

derivation: Coalesce multiple occurrences of the same input.

* guix/derivations.scm (write-derivation)[coalesce-duplicate-inputs]:
  New procedure.
  Use it to process INPUTS.

* tests/derivations.scm ("user of multiple-output derivation"): New
  test.

build: Don't auto-compile tests.

* Makefile.am (TESTS_ENVIRONMENT): Add `--no-auto-compile'.

gnu-build-system: Fix "libdir" and "includedir" for multiple-output drvs.

* guix/build/gnu-build-system.scm (configure): Change `--libdir' and
  `--includedir' to LIBDIR + "/lib" and INCLUDEDIR + "/include",
  respectively.

Upgrade Nix worker protocol.

We were already relying on the new version in `set-build-options', so
this patch fixes that.

* guix/store.scm (%protocol-version): Increase.
  (open-connection)[reserve-space?]: New argument.  Pass it to the
  server when it's recent enough.

derivation: Move sorting code to `write-derivation'.

* guix/derivations.scm (write-derivation): Sorte OUTPUTS, INPUTS,
  SOURCES, and ENV-VARS alphabetically.
  (derivation-hash): Leave INPUTS, SOURCES, and OUTPUTS unsorted.
  (derivation)[env-vars-with-empty-outputs]: Leave ENV-VARS unsorted.