Add support for cross-compiling curl-impersonate.
Cross compiling can now be done using the '--host' flag to the configure
script. This will make sure that all sub-components are cross-compiled.
In addition, compiling for a different system requires explicitly
specifying multiple paths used by curl (e.g. for certificates). These
options were added to the configure script as well.
The build and test CI workflow will now attempt to cross-compile
curl-impersonate to ARM64 (aarch64), and upload this binary to the
GitHub release page.
Add the 'configure' script generated by autoconf and its dependencies to
the repository to save the users from having to run 'autoconf' manually.
