When passing `--build-runtime-with-host-compiler` there's no such executable `wasmkit-cli` in the host toolchain, where it's named `wasmkit` when installed. Let's make that consistent to make it work in both cases.
This patch allows running executable tests with WasmKit. If WasmKit is
not built, fall back to running only non-executable tests. Also add
stdlib and Concurrency executable tests to run.
