Build before debugging with Visual Studio Code.

Build before debugging with Visual Studio Code.

Call make before launching a debug session. Also move from the 'build'
subdirectory to the 'debug' subdirectory to allow for a separate
release build or other configuration.

Change-Id: I6db00a5bb0a707ebbf9c160897852526a8bb73e1
Reviewed-on: https://swiftshader-review.googlesource.com/12528
Reviewed-by: Nicolas Capens <nicolascapens@google.com>
Reviewed-by: Alexis Hétu <sugoi@google.com>
Tested-by: Nicolas Capens <nicolascapens@google.com>