Remove dependence on header file unistd.h.
Remove dependence on header file unistd.h.

Fixes bug in function reportFatalErrorThenExitSuccess by using fwrite
instead of write (a unix posix include file not supported by MSC).

BUG=None
R=stichnot@chromium.org

Review URL: https://codereview.chromium.org/1370323005 .

bkaradzic/SwiftShader,bkaradzic/SwiftShader,google/swiftshader,bkaradzic/SwiftShader,google/swiftshader,bkaradzic/SwiftShader,bkaradzic/SwiftShader,google/swiftshader