utils: Remove special `substitute*' syntax for lists of files.

* guix/build/utils.scm (substitute*): Remove special syntax for
  list-of-files; instead, check whether FILE is `list?' at run time.

* distro/packages/base.scm (gcc-4.7, %binutils-static): Adjust
  accordingly.

distro/packages/base.scm

@@ -759,7 +759,7 @@ BFD (Binary File Descriptor) library, `gprof', `nm', `strip', etc.")
 
                  ;; Tell where to find libstdc++, libc, and `?crt*.o', except
                  ;; `crt{begin,end}.o', which come with GCC.
-                 (substitute* ("gcc/config/gnu-user.h"
+                 (substitute* '("gcc/config/gnu-user.h"
                                 "gcc/config/i386/gnu-user.h"
                                 "gcc/config/i386/gnu-user64.h")
                    (("#define LIB_SPEC (.*)$" _ suffix)
@@ -2310,7 +2310,7 @@ store.")
                    ;; The `-all-static' libtool flag can only be passed
                    ;; after `configure', since configure tests don't use
                    ;; libtool, and only for executables built with libtool.
-                   (substitute* ("binutils/Makefile.in"
+                   (substitute* '("binutils/Makefile.in"
                                   "gas/Makefile.in"
                                   "ld/Makefile.in")
                      (("^LDFLAGS =(.*)$" line)

guix/build/utils.scm

@@ -323,13 +323,15 @@ the complete match, LETTERS is bound to the first sub-expression, and END is
 bound to the last one.
 
 When one of the MATCH-VAR is `_', no variable is bound to the corresponding
-match substring."
-    ((substitute* (file ...) clause ...)
-     (begin
-       (substitute* file clause ...)
-       ...))
+match substring.
+
+Alternatively, FILE may be a list of file names, in which case they are
+all subject to the substitutions."
     ((substitute* file ((regexp match-var ...) body ...) ...)
-     (substitute file
+     (let ()
+       (define (substitute-one-file file-name)
+         (substitute
+          file-name
           (list (cons regexp
                       (lambda (l m+)
                         ;; Iterate over matches M+ and return the
@@ -349,7 +351,13 @@ match substring."
                                       (begin body ...)
                                       (substring l o (match:start m))
                                       r))))))))
-                       ...)))))
+                ...)))
+
+       (match file
+         ((files (... ...))
+          (for-each substitute-one-file files))
+         ((? string? f)
+          (substitute-one-file f)))))))
 
 
 ;;;