And fix the unsupported protover example so it uses a Link protover much
higher than 5.
Part of #25070, bugfix on 0.3.3.1-alpha, which introduced the protover crate.
The code had been using c_char and i8 interchangeably, but it turns
out that c_char is only i8 on platforms where "char" is signed. On
other platforms, c_char is u8.
Fixes bug 24794; bug not on any released Tor.
Instead of using the cwd to specify the location of Cargo.toml, we
use the --manifest-path option to specify its location explicitly.
This works around the bug that isis diagnosed on our jenkins builds.
This adds a couple of configure commands to control whether we're
requiring all dependencies to be available locally (default) or not
(--enable-cargo-online-mode). When building from a tarball, we require
the RUST_DEPENDENCIES variable to point to the local repository of
crates. This also adds src/ext/rust as a git submodule that contains
such a local repository for easy setup.
Passing --enable-cargo-online-mode during configure allows cargo to make
network requests while building Tor or running tests. If this flag is
not supplied, the dependencies need to be available in the form of a
local mirror.
This gives an indication in the log that Tor was built with Rust
support, as well as laying some groundwork for further string-returning
APIs to be converted to Rust
