distro: Configure ld and GCC to not look under /usr & co.

This fixes impurities with non-chroot builds on LFS-style distros.

* distro/packages/base.scm (binutils): Pass `--with-lib-path'.
  (gcc-4.7): Pass `--with-local-prefix'.
* distro/packages/make-bootstrap.scm (%binutils-static): Pass
  `--with-lib-path'.

distro/packages/base.scm

@@ -320,10 +320,12 @@ (define-public binutils
     `(("patch/new-dtags" ,(search-patch "binutils-ld-new-dtags.patch"))))
    (arguments
     `(#:patches (list (assoc-ref %build-inputs "patch/new-dtags"))
+      #:configure-flags '(;; Add `-static-libgcc' to not retain a dependency
+                          ;; on GCC when bootstrapping.
+                          "LDFLAGS=-static-libgcc"
 
-      ;; Add `-static-libgcc' to not retain a dependency on GCC when
-      ;; bootstrapping.
-      #:configure-flags '("LDFLAGS=-static-libgcc")))
+                          ;; Don't search under /usr/lib & co.
+                          "--with-lib-path=/no-ld-lib-path")))
 
    (synopsis "GNU Binutils, tools for manipulating binaries (linker,
 assembler, etc.)")
@@ -358,6 +360,9 @@ (define-public gcc-4.7
           `("--enable-plugin"
             "--enable-languages=c,c++"
             "--disable-multilib"
+
+            "--with-local-prefix=/no-gcc-local-prefix"
+
             ,(let ((libc (assoc-ref %build-inputs "libc")))
                (if libc
                    (string-append "--with-native-system-header-dir=" libc

distro/packages/make-bootstrap.scm

@@ -225,7 +225,7 @@ (define %binutils-static
   (package (inherit binutils)
     (name "binutils-static")
     (arguments
-     `(#:configure-flags '("--disable-gold")
+     `(#:configure-flags '("--disable-gold" "--with-lib-path=/no-ld-lib-path")
        #:strip-flags '("--strip-all")
        #:phases (alist-cons-before
                  'configure 'all-static