rand/rand_unix.c: mask getentropy ELF detection on HP-UX.
rand/rand_unix.c: mask getentropy ELF detection on HP-UX.

Unlike other ELF systems, HP-UX run-time linker fails to detect symbol
availability through weak declaration.

Reviewed-by: Rich Salz <c04971a99e5a9ee80eaab4b1deb37e845b0bd697@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/6583)

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