gnu: cross-base: Externalize cross-gcc arguments.

* gnu/packages/cross-base.scm (cross-gcc-arguments): New procedure.
  (cross-gcc): Use it.  [No functional change.]

gnu/packages/cross-base.scm

@@ -66,33 +66,10 @@
                         `(cons "--with-sysroot=/" ,flags)))))))
     (cross binutils target)))
 
-(define* (cross-gcc target
+(define (cross-gcc-arguments target libc)
-                    #:optional (xbinutils (cross-binutils target)) libc)
+  "Return build system arguments for a cross-gcc for TARGET, using LIBC (which
-  "Return a cross-compiler for TARGET, where TARGET is a GNU triplet.  Use
+may be either a libc package or #f.)"
-XBINUTILS as the associated cross-Binutils.  If LIBC is false, then build a
+  (substitute-keyword-arguments (package-arguments gcc-4.8)
-GCC that does not target a libc; otherwise, target that libc."
-  (package (inherit gcc-4.8)
-    (name (string-append "gcc-cross-"
-                         (if libc "" "sans-libc-")
-                         target))
-    (source (origin (inherit (package-source gcc-4.8))
-              (patches
-               (list (search-patch
-                      "gcc-cross-environment-variables.patch")))))
-
-    ;; For simplicity, use a single output.  Otherwise libgcc_s & co. are not
-    ;; found by default, etc.
-    (outputs '("out"))
-
-    (arguments
-     `(#:implicit-inputs? #f
-       #:modules ((guix build gnu-build-system)
-                  (guix build utils)
-                  (ice-9 regex)
-                  (srfi srfi-1)
-                  (srfi srfi-26))
-
-       ,@(substitute-keyword-arguments (package-arguments gcc-4.8)
     ((#:configure-flags flags)
      `(append (list ,(string-append "--target=" target)
                     ,@(gcc-configure-flags-for-triplet target)
@@ -101,10 +78,9 @@ GCC that does not target a libc; otherwise, target that libc."
                           `(;; Disable features not needed at this stage.
                             "--disable-shared" "--enable-static"
 
-                                   ;; Disable C++ because libstdc++'s
+                            ;; Disable C++ because libstdc++'s configure
-                                   ;; configure script otherwise fails with
+                            ;; script otherwise fails with "Link tests are not
-                                   ;; "Link tests are not allowed after
+                            ;; allowed after GCC_NO_EXECUTABLES."
-                                   ;; GCC_NO_EXECUTABLES."
                             "--enable-languages=c"
 
                             "--disable-threads"   ;libgcc, would need libc
@@ -123,8 +99,8 @@ GCC that does not target a libc; otherwise, target that libc."
     ((#:make-flags flags)
      (if libc
          `(let ((libc (assoc-ref %build-inputs "libc")))
-                   ;; FLAGS_FOR_TARGET are needed for the target libraries to
+            ;; FLAGS_FOR_TARGET are needed for the target libraries to receive
-                   ;; receive the -Bxxx for the startfiles.
+            ;; the -Bxxx for the startfiles.
             (cons (string-append "FLAGS_FOR_TARGET=-B" libc "/lib")
                   ,flags))
          flags))
@@ -150,8 +126,8 @@ GCC that does not target a libc; otherwise, target that libc."
            `(alist-cons-before
              'configure 'set-cross-path
              (lambda* (#:key inputs #:allow-other-keys)
-                     ;; Add the cross Linux headers to CROSS_CPATH, and remove
+               ;; Add the cross Linux headers to CROSS_CPATH, and remove them
-                     ;; them from CPATH.
+               ;; from CPATH.
                (let ((libc  (assoc-ref inputs "libc"))
                      (linux (assoc-ref inputs
                                        "libc/linux-headers")))
@@ -180,11 +156,39 @@ GCC that does not target a libc; otherwise, target that libc."
              ,phases)
            phases)))
     ((#:strip-binaries? _)
-            ;; Disable stripping as this can break binaries, with object files
+     ;; Disable stripping as this can break binaries, with object files of
-            ;; of libgcc.a showing up as having an unknown architecture.  See
+     ;; libgcc.a showing up as having an unknown architecture.  See
      ;; <http://lists.fedoraproject.org/pipermail/arm/2010-August/000663.html>
      ;; for instance.
-            #f))))
+     #f)))
+
+(define* (cross-gcc target
+                    #:optional (xbinutils (cross-binutils target)) libc)
+  "Return a cross-compiler for TARGET, where TARGET is a GNU triplet.  Use
+XBINUTILS as the associated cross-Binutils.  If LIBC is false, then build a
+GCC that does not target a libc; otherwise, target that libc."
+  (package (inherit gcc-4.8)
+    (name (string-append "gcc-cross-"
+                         (if libc "" "sans-libc-")
+                         target))
+    (source (origin (inherit (package-source gcc-4.8))
+              (patches
+               (list (search-patch
+                      "gcc-cross-environment-variables.patch")))))
+
+    ;; For simplicity, use a single output.  Otherwise libgcc_s & co. are not
+    ;; found by default, etc.
+    (outputs '("out"))
+
+    (arguments
+     `(#:implicit-inputs? #f
+       #:modules ((guix build gnu-build-system)
+                  (guix build utils)
+                  (ice-9 regex)
+                  (srfi srfi-1)
+                  (srfi srfi-26))
+
+       ,@(cross-gcc-arguments target libc)))
 
     (native-inputs
      `(("binutils-cross" ,xbinutils)