message: Findursa: specify OpenSSL directory
diff: add_library(ursa UNKNOWN IMPORTED)
  find_package(OpenSSL REQUIRED)
  +get_filename_component(_OPENSSL_INCLUDE_PARENT_DIR ${OPENSSL_INCLUDE_DIR} DIRECTORY)
  +set(OPENSSL_ROOT_DIR ${_OPENSSL_INCLUDE_PARENT_DIR})
  +
  set(URL "https://github.com/hyperledger/ursa/")
  set(VERSION "d425dc2f721659f6bdec50a91d3cb9a1d21ec3f3")
  @@ -17,7 +20,7 @@ externalproject_add(hyperledger_ursa
  GIT_REPOSITORY ${URL}
  GIT_TAG ${VERSION}
  BUILD_IN_SOURCE 1
  - BUILD_COMMAND cargo build --release --no-default-features --features="ffi"
  + BUILD_COMMAND ${CMAKE_COMMAND} -E env OPENSSL_DIR=${OPENSSL_ROOT_DIR} cargo build --release --no-default-features --features="ffi"
  CONFIGURE_COMMAND "" # remove configure step
  UPDATE_COMMAND "" # remove update step
  INSTALL_COMMAND "" # remove install step
  