toolchain: Broaden the executable loader pattern

Some toolchains will produce executables with an interpreter that is e.g:
ld.so.1 (typically a symbolic link). Due to our current LIBC_SPEC_FILE value,
we would not be able to copy this symbolic link/file over to the rootfs and
executables would fail to load. Extend the search pattern to include all
ld*.so* files that could be needed.

Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
(cherry picked from commit 200d932322f3d8c436a67c53f4fbca87f0aab8af)