cc/gcc: disable complibs if not selected

Force gcc to not link with some companion libraries when
there are not needed (because selected-out).

There is no option to tell gcc *not* to build the Graphite and/or
LTO stuff. They *will* be built if gcc finds the suitable companion
libraries. If we do not provide them, but the host has them, then
gcc *will* find them, and link with them.

Consider the following:
- host has suitable PPL and CLooG (eg. Debian Squeeze)
- user wants to build gcc>=4.4
- user de-selects GRAPHITE
- gcc will find the hosts PPL and CLooG, and will use them
- the user moves the toolchain to an older host that does
not have them (eg. Debian Lenny)
- the toolchain fails, when it was properly setup not to

So, explicitly tell gcc *not* to use unneeded companion libs.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@anciens.enib.fr>

 Give preference to target-optimised functions over glibc's ones,

 which in turn ahave precedence over generic ones.

 --- uClibc.orig/libc/Makefile	2005-07-20 08:10:44.000000000 +0200

 +++ uclibc/libc/Makefile	2005-07-28 13:33:40.000000000 +0200

 @@ -59,7 +59,7 @@

  	$(AR) dN 2 $(LIBNAME) $$objs && \

  	$(AR) dN 2 $(LIBNAME) $$objs

  	@for objfile in obj.signal \

 -	                obj.string.generic obj.string.$(TARGET_ARCH) obj.string \

 +	                obj.string obj.string.generic obj.string.$(TARGET_ARCH) \

  	                obj.sysdeps.common obj.sysdeps.$(TARGET_ARCH) ; do \

  		if [ -e $$objfile ] ; then \

  			echo $(AR) $(ARFLAGS) $(LIBNAME) $$objfile ; \