Enhanced privilege escalation on Windows

[retrixe]

• Write a dd reimplementation in the dd folder which can be stopped using stdin.
• Compile it, embed the manifest to run it as admin, and embed it in on Windows.
• On flashing, extract it to a TempDir and execute it as privileged user.
• Once it terminates, delete the TempDir.

[retrixe]

This issue now targets Windows only, since on Linux and macOS, a thin wrapper around dd has been implemented into writer itself. Writer now calls itself with elevated privileges like so: pkexec env DISPLAY=$DISPLAY XAUTHORITY=$XAUTHORITY ./writer dd <file> <drive>. This thin wrapper can be stopped via stdin and is cleaner than this embedded executable approach.

For Windows, we can consider the following:

• Continue with this approach.
• Continue with this approach, but instead of rewriting dd, we reuse dd for Windows and call it from the thin wrapper.
• Port sudo.go to Windows and then write a dd reimplementation to replace the thin wrapper around dd.