scripts: fix finishing the toolchain when download/extract-only is set

In case we only download or extract the sources, do not fail while
finishing the toolchain: the test-suite directory may not exist, so
we can't chmod it.

Also, use safer constructs that won't trigger the 'set -e' in case of
failure (eg.: "[ ... ] && ..." is not safe in case the test fails).

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.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