build-system/{gnu,trivial}: Add a `#:guile' keyword parameter.

* guix/build-system/gnu.scm (package-with-explicit-inputs): New `guile'
  keyword parameter.  Add it to P's arguments, and pass it in recursive
  calls.
  (gnu-build): New `guile' keyword parameter; new `guile-for-build'
  variable.  Pass it as the `#:guile-for-build' parameter of
  `build-expression->derivation'.

* guix/build-system/trivial.scm (trivial-build): Likewise.

1 files changed, 16 insertions, 2 deletions

diff --git a/guix/build-system/trivial.scm b/guix/build-system/trivial.scm
index 1134ae988c..8759cb3f92 100644
--- a/guix/build-system/trivial.scm
+++ b/guix/build-system/trivial.scm
@@ -20,16 +20,30 @@
   #:use-module (guix store)
   #:use-module (guix utils)
   #:use-module (guix derivations)
+  #:use-module (guix packages)
   #:use-module (guix build-system)
+  #:use-module (ice-9 match)
   #:export (trivial-build-system))
 
 (define* (trivial-build store name source inputs
-                        #:key outputs system builder (modules '()))
+                        #:key outputs guile system builder (modules '()))
   "Run build expression BUILDER, an expression, for SYSTEM.  SOURCE is
 ignored."
+  (define guile-for-build
+    (match guile
+      (#f                                         ; the default
+       (let* ((distro (resolve-interface '(distro packages base)))
+              (guile  (module-ref distro 'guile-final)))
+         (package-derivation store guile system)))
+      ((? package?)
+       (package-derivation store guile system))
+      ((? derivation-path?)
+       guile)))
+
   (build-expression->derivation store name system builder inputs
                                 #:outputs outputs
-                                #:modules modules))
+                                #:modules modules
+                                #:guile-for-build guile-for-build))
 
 (define trivial-build-system
   (build-system (name 'trivial)