We use EXEPATH, which points to the root of the MinGW installation
and can be used as a base for translating the unix path to the
executable in the shebang line.
If we're not on MinGW, well, we just throw up our hands and hope
for the best.
Moves platform specific functionality into its own module.
Thanks to @Meralis40 for starting this!
This also gets just building on windows \^_^/
Although a lot of tests still fail (✖╭╮✖)
The `PlatformInterface` trait contains functions which abstract
over platform specific functionality, with implementations for
different platforms behind #[cfg(*)] attributes.
- `make_shebang_command()` constructs a command which will execute
the given script as if by a shebang. On linux this executes the
file, on windows it runs the interpreter directly.
- `set_execute_permission()` sets the execute permission on a
file. This is a nop on windows, since all files are executable.
- `signal_from_exit_status()` extracts the signal a process was
halted by from its exit status, if it was halted by a signal.
