CI/CD to compile the native libraries automatically

[exquo]

I have made a GitHub workflow that automatically compiles the native rust libraries for signal-cli:
https://github.com/exquo/signal-libs-build

From the number of the recent issues in this repo, it is clear that compiling the required rust libraries is a real pain point in installing signal-cli. The workflow above uses GitHub Actions CI/CD infrastructure to pre-compile those libs for most popular platforms. For x86_64 versions of Linux, MacOS and Windows it also patches the native libs into signal-cli. The linux version works with "older" glibc version too (see #643), e.g. Debian 10, Ubuntu 18 and CentOS 7. For other architectures (currently ARMv7, ARM64 and 32 bit Linuxes) it just provides the compiled library files.

All of the files it publishes are produced by the GitHub infrastructure following the steps in the workflow file in the repo's sources. From the security perspective, this means they are not just some opaque binaries coming from somewhere on the internet, but are verifiably and deterministically built by an autonomous process on GitHub's servers.

Feel free to let me know (here or in the repo's issues) if something does not work or if anyone needs binaries for additional platforms.
Cheers!