toolchain: musl: fix symlink for ldd

toolchain: musl: fix symlink for ldd

ld-musl-*.so* is a symlink "broken" for the hostsystem, so wildcard
will skip it, causing LD_MUSL_NAME to empty and the ldd symlink pointing
to ../../lib directly.
This causes sysupgrade failing to copy any linked libaries and
consequently failing to run anything after switching to ram disk.

Fix this by creating a symlink directly pointing to where ld-musl-*.so*
points to.

Signed-off-by: Jonas Gorski <jogo@openwrt.org>
SVN-Revision: 43314