The GdbDebugAgent library is unused and unmaintained, and now it
turns out it doesn't build with Clang, so let's just get rid of it.
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Leif Lindholm <leif.lindholm@linaro.org>