During runtime godot calls chdir() several times. This doesn't really
matter normally but when using tools such as gprof the location of the
profiling data is kind of hard to intuit.
With this PR we simply store the current working directory at start and
restore it once we're almost done exiting.
This doesn't use the OS abstractions as when we need to get the current
workdir we haven't yet initialized it (by necessity). This would break
if we tried to build X11 for windows, but since the X11 target is
hardcoded to use the UNIX abstractions I don't think it matters.
That year should bring the long-awaited OpenGL ES 3.0 compatible renderer
with state-of-the-art rendering techniques tuned to work as low as middle
end handheld devices - without compromising with the possibilities given
for higher end desktop games of course. Great times ahead for the Godot
community and the gamers that will play our games!
