Fix invalid linux tag in checkout config file

Signed-off-by: Anton Kolesov <[email protected]>

Author: anthony-kolesov

config/arc-2015.06-rc1.sh

@@ -4,4 +4,4 @@ gcc=gcc:arc-2015.06-rc1
 gdb=gdb:arc-2015.06-rc1-gdb
 newlib=newlib:arc-2015.06-rc1
 uclibc=uClibc:arc-2015.06-rc1
-linux=linux:arc-2015.06-rc1
+linux=linux:arc-gnu-2015.06-rc1