Require OpenSSL 1.1.0 during CMake.

[daleglass]

Earlier versions don't work with WebRTC, and cause linking errors.

OpenSSL 1.1 is supported in Ubuntu 18.04, although 1.0 can still be installed, which will cause the build to fail. This change ensures the issue is detected right in cmake rather than having the build explode later.

Testing:

Test on Ubuntu 18.04, with OpenSSL 1.0 installed (libssl1.0-dev present, libssl-dev not present)

Before this change, cmake will say something like:

-- Found OpenSSL: /usr/lib64/libcrypto.so (found version "1.0.2n")  

and the build will probably fail with:

../libraries/networking/libnetworking.so: undefined reference to `BIO_meth_new'
../libraries/networking/libnetworking.so: undefined reference to `OPENSSL_init_crypto'
../libraries/networking/libnetworking.so: undefined reference to `OPENSSL_init_ssl'
../libraries/networking/libnetworking.so: undefined reference to `BIO_meth_set_write'
../libraries/networking/libnetworking.so: undefined reference to `BIO_set_data'
../libraries/networking/libnetworking.so: undefined reference to `BIO_meth_set_ctrl'
../libraries/networking/libnetworking.so: undefined reference to `BIO_meth_set_puts'
../libraries/networking/libnetworking.so: undefined reference to `BIO_get_data'
../libraries/networking/libnetworking.so: undefined reference to `BIO_set_init'
../libraries/networking/libnetworking.so: undefined reference to `BIO_set_shutdown'
../libraries/networking/libnetworking.so: undefined reference to `BIO_meth_set_create'
../libraries/networking/libnetworking.so: undefined reference to `HMAC_CTX_free'
../libraries/networking/libnetworking.so: undefined reference to `SSL_CTX_up_ref'
../libraries/networking/libnetworking.so: undefined reference to `EVP_MD_CTX_reset'
../libraries/networking/libnetworking.so: undefined reference to `EVP_MD_CTX_new'
../libraries/networking/libnetworking.so: undefined reference to `BIO_meth_set_destroy'
../libraries/networking/libnetworking.so: undefined reference to `EVP_MD_CTX_free'
../libraries/networking/libnetworking.so: undefined reference to `SSL_session_reused'
../libraries/networking/libnetworking.so: undefined reference to `X509_getm_notBefore'
../libraries/networking/libnetworking.so: undefined reference to `TLS_method'
../libraries/networking/libnetworking.so: undefined reference to `EVP_PKEY_up_ref'
../libraries/networking/libnetworking.so: undefined reference to `X509_up_ref'
../libraries/networking/libnetworking.so: undefined reference to `HMAC_CTX_new'
../libraries/networking/libnetworking.so: undefined reference to `X509_getm_notAfter'
../libraries/networking/libnetworking.so: undefined reference to `X509_STORE_CTX_get0_cert'
../libraries/networking/libnetworking.so: undefined reference to `BIO_meth_set_read'

With this change, cmake will say:

-- Found OpenSSL: /usr/lib64/libcrypto.so (found suitable version "1.1.1l", minimum required is "1.1.0")  

And should work correctly.

This should make no difference at all on any recent Linux distribution.

[vircadia-build-notifier]

The following links are available:
build (macOS-10.15, client)

• https://athena-public.s3.eu-west-3.amazonaws.com/builds/PR/vircadia_vircadia/PR1436/Vircadia-Interface-PR1436-c5046ab-_732b32b6.dmg

build (ubuntu-18.04, full)

• https://athena-public.s3.eu-west-3.amazonaws.com/builds/PR/vircadia_vircadia/PR1436/Vircadia-PR1436-c5046ab-.tar_732b32b6.gz
• https://athena-public.s3.eu-west-3.amazonaws.com/builds/PR/vircadia_vircadia/PR1436/Vircadia-PR1436-c5046ab-_732b32b6.sh
• https://athena-public.s3.eu-west-3.amazonaws.com/builds/PR/vircadia_vircadia/PR1436/Vircadia-PR1436-c5046ab-.tar_732b32b6.Z

build (macOS-10.15, full)

• https://athena-public.s3.eu-west-3.amazonaws.com/builds/PR/vircadia_vircadia/PR1436/Vircadia-PR1436-c5046ab-_732b32b6.dmg

build (windows-latest, full)

• https://athena-public.s3.eu-west-3.amazonaws.com/builds/PR/vircadia_vircadia/PR1436/Vircadia-PR1436-c5046ab-_732b32b6.exe