build file templates: have targets for all shared library names

We only had targets for the "simple" shared library names (libfoo.so
and not libfoo.so.x.y on Unix, import library libfoo.lib but not
libfoo.dll on Windows).  This has created some confusion why it wasn't
possible to rebuild the less "simple" name directly (just as an
example, someone who mistook the import library on Windows for a
static library, removed the DLL and then found it was difficult to
rebuild directly), so we change the target to include all possible
names.

Reviewed-by: Tim Hudson <tjh@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/7451)

(cherry picked from commit d8cac50b)