devtool: Allow for target specification
devtool: Allow for target specification

This patch looks for a --target flag and passes it to cargo falling back
to the default target that is detected by the system.

Fixes: https://github.com/firecracker-microvm/firecracker/issues/1160

Signed-off-by: Garrett Squire <af6d0dbbb7603d297f8e6b7b2a6a2b8732fee13d@gmail.com>

firecracker-microvm/firecracker,firecracker-microvm/firecracker,firecracker-microvm/firecracker,firecracker-microvm/firecracker,firecracker-microvm/firecracker