scripts: do not provide to-sysroot include symlink

Do not provide the PREFIX/TUPLE/include -> SYSROOT/usr/include symlink,
and let gcc install its dependable C++ headers were it sees fit to
install them.

See the test by Anthony (by the end of the messages):
http://sourceware.org/ml/crossgcc/2010-10/msg00129.html
http://sourceware.org/ml/crossgcc/2010-10/msg00134.html

See also the comment by Arnaud:
http://sourceware.org/ml/crossgcc/2010-10/msg00157.html

Reported-by: Anthony Foiani <anthony.foiani@gmail.com>
Signed-off-by: "Yann E. MORIN" <yann.morin.1998@anciens.enib.fr>

--- gcc-4.3.2.orig/gcc/config/arm/linux-eabi.h	2009-09-08 23:46:44.000000000 +0200

+++ gcc-4.3.2/gcc/config/arm/linux-eabi.h	2009-09-08 23:46:51.000000000 +0200

@@ -44,7 +44,7 @@

    The ARM10TDMI core is the default for armv5t, so set

    SUBTARGET_CPU_DEFAULT to achieve this.  */

 #undef  SUBTARGET_CPU_DEFAULT

-#define SUBTARGET_CPU_DEFAULT TARGET_CPU_arm10tdmi

+#define SUBTARGET_CPU_DEFAULT TARGET_CPU_arm9tdmi

 /* TARGET_BIG_ENDIAN_DEFAULT is set in

    config.gcc for big endian configurations.  */