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>

timezone data has been split into the package sys-libs/timezone-data

diff -durN glibc-2.10.1.orig/Makeconfig glibc-2.10.1/Makeconfig

--- glibc-2.10.1.orig/Makeconfig	2009-11-13 00:50:13.000000000 +0100

+++ glibc-2.10.1/Makeconfig	2009-11-13 00:50:41.000000000 +0100

@@ -919,7 +919,7 @@

 	      stdlib stdio-common libio malloc string wcsmbs time dirent    \

 	      grp pwd posix io termios resource misc socket sysvipc gmon    \

 	      gnulib iconv iconvdata wctype manual shadow gshadow po argp   \

-	      crypt nss localedata timezone rt conform debug		    \

+	      crypt nss localedata rt conform debug		    \

 	      $(add-on-subdirs) $(dlfcn) $(binfmt-subdir)

 ifndef avoid-generated