Add a new serial:// protocol along with SerialPort that provides a new
API to open serial ports. The URL consists of serial device path
followed by URL-style options, e.g.:
serial:///dev/ttyS0?baud=115200&parity=even
If no options are provided, the serial port is only set to raw mode
and the other attributes remain unchanged. Attributes provided via
options are modified to the specified values. Upon closing the serial
port, its original attributes are restored.
Differential Revision: https://reviews.llvm.org/D111355
Fix the termination of "process connect" (and "gdb-remote") to kill
the process rather than attempting to disconnect the platform.
The latter only results in an error since we did not use "platform
connect", and apparently process-level connections (at least via
gdb-remote) do not really support disconnecting.
Differential Revision: https://reviews.llvm.org/D110996