guix: Add elm-build-system.

* gnu/packages/patches/elm-offline-package-registry.patch: New file.
* gnu/local.mk (dist_patch_DATA): Add it.
* gnu/packages/elm.scm (elm): Use it.
* guix/build-system/elm.scm, guix/build/elm-build-system.scm,
tests/elm.scm: New files.
* Makefile.scm (MODULES, SCM_TESTS): Add them.
* doc/guix.texi (Build Systems): Document 'elm-build-system'.
* doc/contributing.texi (Elm Packages): New section. Document naming
conventions and utilities.

Signed-off-by: Ludovic Courtès <ludo@gnu.org>

1 files changed, 3 insertions, 0 deletions

diff --git a/Makefile.am b/Makefile.am
index 85a22be99cc..9ca92c407c1 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -141,6 +141,7 @@ MODULES =					\
   guix/build-system/cmake.scm                   \
   guix/build-system/dub.scm                     \
   guix/build-system/dune.scm                    \
+  guix/build-system/elm.scm                     \
   guix/build-system/emacs.scm                   \
   guix/build-system/font.scm                    \
   guix/build-system/go.scm                      \
@@ -192,6 +193,7 @@ MODULES =					\
   guix/build/cmake-build-system.scm             \
   guix/build/dub-build-system.scm               \
   guix/build/dune-build-system.scm              \
+  guix/build/elm-build-system.scm               \
   guix/build/emacs-build-system.scm             \
   guix/build/meson-build-system.scm             \
   guix/build/minify-build-system.scm            \
@@ -472,6 +474,7 @@ SCM_TESTS =					\
   tests/derivations.scm                 \
   tests/discovery.scm                           \
   tests/egg.scm                         \
+  tests/elm.scm                         \
   tests/elpa.scm                                \
   tests/file-systems.scm                        \
   tests/gem.scm                         \