libclntsh.so* and libocci.so* are symlinks to the latest version.
By using `install`, these are all dereferenced and duplicated.
Let's avoid that, and shrink the lib output from 621M to 226M.
This wasn't about PECL::oci8 in first place, but DBD-Oracle.
In the current version of oracle-instantclient, a libclntsh.so is
shipped, so DBD-Oracle is happy.
It's now possible to download Oracle Instant Client without having to
click a checkbox to agree to the license, and then log in with an Oracle
account to start the download, at least on Linux (for now).
Darwin still seems to be at 18.1, and version numbers haven't been that
aligned recently, so allow different version numbers per platform.
Split `buildCommand`, provide `unpackCmd` and add `installPhase`.
Use autoPatchelfHook, we can get rid of all the manual hacking around
with patchelf.
Use install to install to $out
