Fix build error when installing toolchain on top of existing

There was an error when installing linux-uclibc toolchain in case
installation directory already contained previous toolchain versions.
Creatign of symlinks failed. This patch adds option -f to the `ln' to avoid
this problem.

Signed-off-by: Anton Kolesov <Anton.Kolesov@synopsys.com>
Fix build error for big endian toolchain

Build of big endian linux-uclibc toolchain failed because there was a
hardcoded target triplet of little endian toolchain.

Signed-off-by: Anton Kolesov <Anton.Kolesov@synopsys.com>