Right now F* cannot be bootstrapped on Windows, but a bootstrapped F* source package can be produced on Linux, and then that source package can be compiled on Windows.

This PR allows building an EverParse binary package from a F* source package. This will work both on Linux and Windows.

This PR also updates the release process to build a binary release from a F* source package. Once this PR is merged into master and master is merged into the _release branch, the release.sh script will build a F* source package on Linux and commit its contents to the EverParse _release branch. Thus, the EverParse binary package will be able to be rebuilt from there without the need to retrieve F* source packages from GitHub's out-of-repository storage mechanisms (build/release artifacts, etc.)

To this end, it is important that the release be performed on Linux first, before Windows, since F* cannot be bootstrapped on Windows.

This PR also introduces a test mode for releases: when the EVERPARSE_TEST_RELEASE environment variable is set to some nonempty value, release.sh all steps except git push and GitHub artifact uploads.