Closes ticket 26372.

These appear to work for me.

We need this trick because some of our Rust tests depend on our C
code, which in turn depend on other native libraries, which thereby
pulls a whole mess of our build system into "cargo test".

To solve this, we add a build script (build.rs) to set most of the
options that we want based on the contents of config.rust.  Some
options can't be set, and need to go to the linker directly: we use
a linker replacement (link_rust.sh) for these.  Both config.rust and
link_rust.sh are generated by autoconf for us.

This patch on its own should enough to make the crypto test build,
but not necessarily enough to make it pass.

This reverts commit 70d91bd0.

This was already added to LIBTOR_A_SOURCES; it doesn't need to get
added again.

Fixes bug 26402. Bugfix on 0.3.4.1-alpha.

Set rustc flags to treat warnings as fatal if configured with
--enable-warnings.

 * FIXES #24659: https://bugs.torproject.org/24659

The --disable-module-* configure option removes code from the final binary but
we still build the unit tests with the disable module(s) so we can actually
test that code path all the time and not forget about it.
Signed-off-by: David Goulet <dgoulet@torproject.org>

Make our build system support a disable dirauth module option. It can only be
disabled explicitly with:

  $ ./configure --disable-module-dirauth

If *not* specified that is enabled, an automake conditional variable is set to
true and a defined value for the C code:

  AM_CONDITIONAL: BUILD_MODULE_DIRAUTH
  AC_DEFINE: HAVE_MODULE_DIRAUTH=1

This introduces the dirauth/ module directory in src/or/ for which .c files
are only compiled if the BUILD_MODULE_DIRAUTH is set.

All the header files are compiled in regardless of the support so we can use
the alternative entry point functions of the dirauth subsystem.
Signed-off-by: David Goulet <dgoulet@torproject.org>

When openssl is built with no-deprecated, the TLSv1_1_method()
function isn't visible in the headers.  That's sad, because that
method is what we were looking at.

Instead, we now look at SSL_CIPHER_get_id(), which is present in
OpenSSL 1.0.1 and later, which is _not_ deprecated, and which is
also present in LibreSSL.

Fixes ticket 25353.  Not a bugfix exactly -- we never really worked
with this configuration.

By default, we want to look at the crates directory of the
submodule, not the toplevel of the submodule.  Fixes bug 25679;
bugfix on 0.3.3.1-alpha.

Georg Koppen authored Mar 28, 2018 and Nick Mathewson committed Mar 28, 2018

When merging the patches for #25310 the libc version requirement in
`GettingStartedRust.md` and `configure.ac` did not get updated to the
now needed 0.2.39.

Without this fix, we were just getting SRCDIR=`pwd`, which naturally
was breaking out-of-tree builds.

Bugfix on becae4c9; bug not in any
released Tor.

Fixes bug 25474; bugfix on 0.3.2.5-alpha.