I am afraid it is not as simple as re-adding the build-dependency on libssh2-1-dev. It was not removed by mistake, but as an explicit decision, per bug #175891.
For curl to be able to depend on libssh2 it too would have to be in Main. See https://wiki.ubuntu.com/UbuntuMainInclusionRequirements for more information.
I am afraid it is not as simple as re-adding the build-dependency on libssh2-1-dev. It was not removed by mistake, but as an explicit decision, per bug #175891.
For curl to be able to depend on libssh2 it too would have to be in Main. See https:/ /wiki.ubuntu. com/UbuntuMainI nclusionRequire ments for more information.