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 -urN glibc-2.12.1-orig/posix/sys/types.h glibc-2.12.1/posix/sys/types.h

--- glibc-2.12.1-orig/posix/sys/types.h	2010-12-13 11:47:26.000000000 +0100

+++ glibc-2.12.1/posix/sys/types.h	2011-03-29 14:16:00.374064708 +0200

@@ -114,7 +114,10 @@

 #ifdef	__USE_BSD

 # ifndef __daddr_t_defined

 typedef __daddr_t daddr_t;

+#  if ! defined(caddr_t) && ! defined(__caddr_t_defined)

 typedef __caddr_t caddr_t;

+#   define __caddr_t_defined

+#  endif

 #  define __daddr_t_defined

 # endif

 #endif

diff -urN glibc-2.12.1-orig/sunrpc/rpc/types.h glibc-2.12.1/sunrpc/rpc/types.h

--- glibc-2.12.1-orig/sunrpc/rpc/types.h	2010-12-13 11:47:26.000000000 +0100

+++ glibc-2.12.1/sunrpc/rpc/types.h	2011-03-29 14:16:32.988910439 +0200

@@ -80,7 +80,10 @@

 #endif

 #ifndef __daddr_t_defined

 typedef __daddr_t daddr_t;

+# if ! defined(caddr_t) && ! defined(__caddr_t_defined)

 typedef __caddr_t caddr_t;

+#  define __caddr_t_defined

+# endif

 # define __daddr_t_defined

 #endif