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 duma_2_5_14.orig/Makefile duma_2_5_14/Makefile

--- duma_2_5_14.orig/Makefile	2008-06-17 10:30:40.000000000 +0200

+++ duma_2_5_14/Makefile	2008-06-17 10:30:17.000000000 +0200

@@ -228,9 +228,13 @@

 	dumatest.c tstheap.c thread-test.c testmt.c dumatestpp.cpp testoperators.cpp \

 	createconf.c

-OBJECTS = dumapp.o duma.o sem_inc.o print.o

+OBJECTS = duma.o sem_inc.o print.o

+SO_OBJECTS = duma_so.o sem_inc_so.o print_so.o

-SO_OBJECTS = dumapp_so.o duma_so.o sem_inc_so.o print_so.o

+ifeq ($(DUMA_CPP),1)

+OBJECTS += dumapp.o

+SO_OBJECTS += dumapp_so.o

+endif

 all:	libduma.a tstheap$(EXEPOSTFIX) dumatest$(EXEPOSTFIX) thread-test$(EXEPOSTFIX) testmt$(EXEPOSTFIX) dumatestpp$(EXEPOSTFIX) testoperators$(EXEPOSTFIX) $(DUMA_DYN_DEPS)