software/beremiz-ide: set OPENSSL_ROOT_DIR to slapos' openssl

otherwise it probably uses system's openssl.

Setting rpath seems not needed because we are using
-DBUILD_SHARED_LIBS=OFF here.
5 jobs for 1.0
Status Job ID Name Coverage
  External
passed ERP5.StandaloneDeploymentScriptTest-Debian.Buster

failed ERP5.StandaloneDeploymentScriptTest-Debian.Buster.Master

passed SlapOS-Master.StandaloneDeploymentScriptTest-Debian.Buster

failed Wendelin.StandaloneDeploymentScriptTest-Debian.Buster.Master

passed Wendelin.StandaloneDeploymentScriptTest-Debian.Stretch