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 gcc-4.5.2.orig/libjava/Makefile.in gcc-4.5.2/libjava/Makefile.in

--- gcc-4.5.2.orig/libjava/Makefile.in	2010-12-16 13:49:03.000000000 +0100

+++ gcc-4.5.2/libjava/Makefile.in	2010-12-29 23:02:41.000000000 +0100

@@ -9463,6 +9463,9 @@

 ecjx$(EXEEXT): $(ecjx_OBJECTS) $(ecjx_DEPENDENCIES) 

 	@rm -f ecjx$(EXEEXT)

 	$(ecjx_LINK) $(ecjx_OBJECTS) $(ecjx_LDADD) $(LIBS)

+ecjx.$(OBJEXT): $(ecjx_SOURCES)

+	@rm -f ecjx.$(OBJEXT)

+	$(CC_FOR_BUILD) $(BUILD_CFLAGS) -c -o $@ $<

 gappletviewer$(EXEEXT): $(gappletviewer_OBJECTS) $(gappletviewer_DEPENDENCIES) 

 	@rm -f gappletviewer$(EXEEXT)

 	$(gappletviewer_LINK) $(gappletviewer_OBJECTS) $(gappletviewer_LDADD) $(LIBS)