scripts/libc: do not build add-ons by default

Currently, no --enable-add-ons option is passed to libc configure when
"$(do_libc_add_ons_list ,)" is empty, which makes configure automatically search
for present add-ons. In that case, all present add-ons are built, although
no add-on was selected by the user in the config. Moreover, this can make the
configure fail if some non-standard add-ons like eglibc-localedef are present.

This behavior also leads to an inconsistency from a user point of view between
the following cases:
- LIBC_ADDONS_LIST="", LIBC_GLIBC_USE_PORTS=n and THREADS="none" in the config,
which makes "$(do_libc_add_ons_list ,)" return "", so all present add-ons
are built.
- LIBC_ADDONS_LIST="", LIBC_GLIBC_USE_PORTS=n and THREADS!="none" in the
config, which makes "$(do_libc_add_ons_list ,)" return the add-on supporting
the chosen threading implementation, e.g. "nptl", so only this add-on is
built.

This patch disables the building of all add-ons in that case.

It is still possible to build all present add-ons by adding --enable-add-ons to
LIBC_GLIBC_EXTRA_CONFIG_ARRAY.

Signed-off-by: "Benoît THÉBAUDEAU" <benoit.thebaudeau@advansee.com>

diff -dur glibc-cvs-2.9.orig/debug/readlink_chk.c glibc-cvs-2.9/debug/readlink_chk.c

--- glibc-cvs-2.9.orig/debug/readlink_chk.c	2005-03-01 01:41:15.000000000 +0100

+++ glibc-cvs-2.9/debug/readlink_chk.c	2009-06-01 10:59:37.000000000 +0200

@@ -25,7 +25,7 @@

 ssize_t

-__readlink_chk (const char *path, void *buf, size_t len, size_t buflen)

+__readlink_chk (const char *path, char *buf, size_t len, size_t buflen)

 {

   if (len > buflen)

     __chk_fail ();

diff -dur glibc-cvs-2.9.orig/debug/readlinkat_chk.c glibc-cvs-2.9/debug/readlinkat_chk.c

--- glibc-cvs-2.9.orig/debug/readlinkat_chk.c	2006-04-24 18:56:12.000000000 +0200

+++ glibc-cvs-2.9/debug/readlinkat_chk.c	2009-06-01 11:07:26.000000000 +0200

@@ -21,7 +21,7 @@

 ssize_t

-__readlinkat_chk (int fd, const char *path, void *buf, size_t len,

+__readlinkat_chk (int fd, const char *path, char *buf, size_t len,

 		  size_t buflen)

 {

   if (len > buflen)