This was moved to a separate step with 0ff939585e ("travis: Bump tpm2-tss
to 2.4.1") so packages are installed before these dependencies are built.
However, on LGTM, packages can't be installed explicitly, so `deps` is
a no-op and we still have to list some dependencies in the config.
The build system is a bit limited, only the repository directory and
LGTM_WORKSPACE is writable. sudo doesn't work at all, for others we
don't have enough permission.