build-system/gnu: Implement cross build.

* guix/build-system/gnu.scm (inputs-search-paths): New procedure.
  (standard-search-paths): Use it.
  (expand-inputs): New procedure.
  (standard-inputs): Use it.
  (standard-cross-packages, standard-cross-inputs,
  standard-cross-search-paths, gnu-cross-build): New procedures.
  (gnu-build-system): Set `cross-build' field to `gnu-cross-build'.
* gnu/packages/cross-base.scm: Export `cross-gcc', `cross-binutils', and
  `cross-libc'.
* guix/build/gnu-cross-build.scm: New file.
* Makefile.am (MODULES): Add it.

1 files changed, 4 insertions, 1 deletions

diff --git a/gnu/packages/cross-base.scm b/gnu/packages/cross-base.scm
index 06e66541de0..22878a20b07 100644
--- a/gnu/packages/cross-base.scm
+++ b/gnu/packages/cross-base.scm
@@ -29,7 +29,10 @@
   #:use-module (guix build-system trivial)
   #:use-module (srfi srfi-1)
   #:use-module (srfi srfi-26)
-  #:use-module (ice-9 match))
+  #:use-module (ice-9 match)
+  #:export (cross-binutils
+            cross-libc
+            cross-gcc))
 
 (define (cross p target)
   (package (inherit p)