[BUG] Entering interactive mode breaks UART input

[dkaszews]

I am playing around with UART in bare metal mode and have noticed really weird behavior. When first starting any program that reads from UART, any input is echoed into terminal and buffered until a return key is pressed. However, if you enter interactive mode and resume with rs, the behavior changes - input is not echoed anymore and passed intermediately to the assembly.

For reproduction, you can use example at https://github.com/Benjamin-Davies/spark-minimal-uart (remove first line from link.ld script, as some linkers don't like it).