This adds the necessary structs and the `ReadBuildInfo()` function to
the runtime/debug module to allow to compile code that tries to access
it.
The stub itself returns ok=false, so that calling code should not try
to read from the nil pointer that is returned instead of the actual
BuildInfo struct.
This package does not implement any methods, which is of course not
useful. However, by creating this package in advance it's possible to
see the next issue that's preventing something from building in TinyGo.
Motivated by: https://github.com/tinygo-org/tinygo/issues/1634
