gnu: guile-static: Provide a libgc variant with statically built libraries.

* gnu/packages/bdw-gc.scm (libgc/static-libs): New public variable.
* gnu/packages/make-bootstrap.scm (%guile-static)[propagated-inputs]: Change
from LIBGC to LIBGC/STATIC-LIBS.

gnu/packages/bdw-gc.scm

@@ -24,6 +24,7 @@ (define-module (gnu packages bdw-gc)
   #:use-module (guix licenses)
   #:use-module (guix packages)
   #:use-module (guix download)
+  #:use-module (guix utils)
   #:use-module (guix build-system gnu)
   #:use-module (gnu packages pkg-config)
   #:use-module (gnu packages hurd))
@@ -84,6 +85,14 @@ (define-public libgc
 
    (license (x11-style (string-append home-page "license.txt")))))
 
+;; TODO: Add a static output in libgc in the next rebuild cycle.
+(define-public libgc/static-libs
+  (package/inherit
+   libgc
+   (arguments (substitute-keyword-arguments (package-arguments libgc)
+                ((#:configure-flags flags ''())
+                 `(cons "--enable-static" ,flags))))))
+
 (define-public libgc-7
   (package
    (inherit libgc)

gnu/packages/make-bootstrap.scm

@@ -699,7 +699,7 @@ (define %guile-static
                      ,@(package-inputs guile-2.2)))
 
                   (propagated-inputs
-                   `(("bdw-gc" ,libgc)
+                   `(("bdw-gc" ,libgc/static-libs)
                      ,@(alist-delete "bdw-gc"
                                      (package-propagated-inputs guile-2.0))))
                   (arguments