scripts: add option to only use the mirror

Currently, if downloads are forbidden, the mirror is still tried for.

Change this way:
- if downlaods forbidden, do not try neither upstream locations nor mirror
- add option to only use the mirror, and avoid upstream locations

Signed-off-by: Austin Morton <austinpmorton@gmail.com>
[yann.morin.1998@free.fr: broaden the if USE_MIRRORto enclode mirror location]
Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>

diff -durN gcc-4.4.5.orig/gcc/config/netbsd-elf.h gcc-4.4.5/gcc/config/netbsd-elf.h

--- gcc-4.4.5.orig/gcc/config/netbsd-elf.h	2007-09-03 18:14:04.000000000 +0200

+++ gcc-4.4.5/gcc/config/netbsd-elf.h	2010-10-09 22:59:57.000000000 +0200

@@ -82,6 +82,7 @@

 #define NETBSD_LINK_SPEC_ELF \

   "%{assert*} %{R*} %{rpath*} \

    %{shared:-shared} \

+   %{symbolic:-Bsymbolic} \

    %{!shared: \

      -dc -dp \

      %{!nostdlib: \