* Remove the dependency to the rust frontend and library from the test
driver. Tests are compiled and run as standalone programs.
* Add diagnostics for the initial cargo run for the dependencies.
Collect all tests are build time in build.rs and generate Rust code that
uses #[test] annotated functions. This gives nice reporting and the
ability to run individual tests.
* Fix text-file-busy error when running the binary by replacing the use
of named temp file with simply using the input source file and the
extension replaced. A scope guard make sure to also delete the binary.
* Fix hard-coded library dependencies by sharing code with the cmake
xtask that needs the same list.
This extracts a compiler command line from the cc crate, runs the
compiler and tries to run the resulting binary. Unfortunately the latter
fails still.
