Configure: add shared() to facilitate shared-specific flags.
Configure: add shared() to facilitate shared-specific flags.

This allows to specify flags specific to shared build, e.g.
'bin_lflags => shared("-Wl,-bsvr4")'.

Reviewed-by: Rich Salz <c04971a99e5a9ee80eaab4b1deb37e845b0bd697@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/6453)

openssl/openssl,openssl/openssl,openssl/openssl,openssl/openssl,openssl/openssl,openssl/openssl