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-4.2.0.orig/libstdc++-v3/include/c_std/std_cstdio.h	2006-12-07 10:33:51.000000000 +0100

+++ gcc-4.2.0/libstdc++-v3/include/c_std/std_cstdio.h	2007-05-20 01:05:38.000000000 +0200

@@ -144,7 +144,7 @@

 _GLIBCXX_END_NAMESPACE

-#if _GLIBCXX_USE_C99

+#if _GLIBCXX_USE_C99 || defined(__UCLIBC__)

 #undef snprintf

 #undef vfscanf