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 binutils-2.20.1.orig/ld/emulparams/elf_i386.sh binutils-2.20.1/ld/emulparams/elf_i386.sh

 --- binutils-2.20.1.orig/ld/emulparams/elf_i386.sh	2009-07-29 16:59:23.000000000 +0200

 +++ binutils-2.20.1/ld/emulparams/elf_i386.sh	2010-08-17 19:32:12.000000000 +0200

 @@ -13,3 +13,13 @@

  NO_SMALL_DATA=yes

  SEPARATE_GOTPLT=12

  IREL_IN_PLT=

 +

 +# In Gentoo, we install 32bit libs into /lib32 in an

 +# ABI setup with amd64/x86

 +case "$target" in

 +  x86_64*-linux*)

 +    case "$EMULATION_NAME" in

 +      *i386*) LIBPATH_SUFFIX=32  ;;

 +    esac

 +  ;;

 +esac