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-3.4.6.orig/gcc/config/arm/arm.c gcc-3.4.6/gcc/config/arm/arm.c

 --- gcc-3.4.6.orig/gcc/config/arm/arm.c	2007-08-15 22:57:51.000000000 +0200

 +++ gcc-3.4.6/gcc/config/arm/arm.c	2007-08-15 22:57:51.000000000 +0200

 @@ -4572,6 +4572,10 @@

  int

  adjacent_mem_locations (rtx a, rtx b)

  {

 +  /* We don't guarantee to preserve the order of these memory refs.  */

 +  if (volatile_refs_p (a) || volatile_refs_p (b))

 +    return 0;

 +

    if ((GET_CODE (XEXP (a, 0)) == REG

         || (GET_CODE (XEXP (a, 0)) == PLUS

  	   && GET_CODE (XEXP (XEXP (a, 0), 1)) == CONST_INT))

 @@ -4611,6 +4615,17 @@

  	return 0;

        val_diff = val1 - val0;

 +

 +      if (arm_ld_sched)

 +	{

 +	  /* If the target has load delay slots, then there's no benefit

 +	     to using an ldm instruction unless the offset is zero and

 +	     we are optimizing for size.  */

 +	  return (optimize_size && (REGNO (reg0) == REGNO (reg1))

 +		  && (val0 == 0 || val1 == 0 || val0 == 4 || val1 == 4)

 +		  && (val_diff == 4 || val_diff == -4));

 +	}

 +

        return ((REGNO (reg0) == REGNO (reg1))

  	      && (val_diff == 4 || val_diff == -4));

      }