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 -durN glibc-2.12.1.orig/elf/dl-lookup.c glibc-2.12.1/elf/dl-lookup.c

--- glibc-2.12.1.orig/elf/dl-lookup.c	2009-03-30 23:14:32.000000000 +0200

+++ glibc-2.12.1/elf/dl-lookup.c	2009-11-13 00:51:36.000000000 +0100

@@ -301,6 +301,12 @@

 	      /* FALLTHROUGH */

 	    case STB_GLOBAL:

	    success:

+#ifdef __mips__

+	      /* HACK: MIPS marks its lazy evaluation stubs with SHN_UNDEF

+		 symbols, we skip them. */

+	      if (sym->st_shndx == SHN_UNDEF)

+		break;

+#endif

 	      /* Global definition.  Just what we need.  */

 	      result->s = sym;

 	      result->m = (struct link_map *) map;