[Patch v2] Add non-standard compiler prefix support

[Programmingkid]

This simplifies the patch even more. The $PREFIX variable has been changed to 
$CROSS_COMPILER. It is much more intuitive this way. Thank you Lennart for the
suggestion.

Signed-off-by: John Arbuckle

Index: config/scripts/switch-arch
===================================================================
--- config/scripts/switch-arch	(revision 1335)
+++ config/scripts/switch-arch	(working copy)
@@ -99,7 +99,8 @@

select_prefix()
{
-    for TARGET in ${1}-unknown-linux-gnu- ${1}-linux-gnu- ${1}-linux- ${1}-elf- ${1}-eabi-
+    # if the user specified the cross compiler like this: CROSS_COMPILER=ppc-elf- ./switch-arch ppc
+    for TARGET in ${1}-unknown-linux-gnu- ${1}-linux-gnu- ${1}-linux- ${1}-elf- ${1}-eabi- $CROSS_COMPILER
    do
        if type ${TARGET}gcc > /dev/null 2>&1
        then