Fix shared library dependencies verification on some platforms (#8349)

Fix shared library dependencies verification on some platforms (#8349)

The existing way of verifying shared library dependencies, used for
System.Globalization.Native.so, doesn't work on platforms that don't
have ldd or where ldd doesn't support the `-r` option.
This change makes the check happen on non-Alpine Linux only for now.
It also refactors the way the check is performed. Instead of doing it
post build in the build.sh, it is now performed as a postbuild phase
of the System.Globalization.Native target and it is also generalized
so that we can easily add such verification to other build targets.
The new verify-so.sh script is also used in corefx.