regression: tinygo apps crash in one wasi runtime if argc == 0?

[dkegel-fastly]

Since 7b761fa,
tinygo apps crash on one wasm runtime. It seems the runtime used by my employer does not provide argv[0].
I could not reproduce the problem with wasmtime or wasmer, but the problem is quite reproducible in our environment.

I also tested on mac and linux, using execve to run a tinygo app without argv[0], but that worked without a crash;
linux actually does allow running with no argv[0], believe it or not, but that didn't cause a problem as it did with wasi.

The change to tinygo to avoid the crash in the wasi case is, well, tiny. Pull request coming.

[deadprogram]

Since this issue was introduced in-between releases I am going to mark as closed. Thanks @dkegel-fastly for the report and the fix!