bc: changed to be build at cross stage if requested

This is needed because the linux kernel needs bc at build time.

base/bc/bc.desc

@@ -3,7 +3,7 @@
 [COPY] This copyright note is auto-generated by ./scripts/Create-CopyPatch.
 [COPY]
 [COPY] Filename: package/.../bc/bc.desc
-[COPY] Copyright (C) 2006 The OpenSDE Project
+[COPY] Copyright (C) 2006 - 2014 The OpenSDE Project
 [COPY] Copyright (C) 2004 - 2006 The T2 SDE Project
 [COPY] Copyright (C) 1998 - 2004 Clifford Wolf
 [COPY]
@@ -37,7 +37,7 @@
 [L] GPL
 [S] Stable
 [V] 1.06
-[P] X -----5---9 109.500
+[P] X -?---5---9 109.500
 
 [D] 806514776 bc-1.06.tar.gz ftp://ftp.gnu.org/pub/gnu/bc/