Use the ErrorOr pattern with the Core::System wrappers to propagate more
errors from the TerminalWrapper.
The run_command method, when called with WaitForExit::Yes now returns an
error on command failure.
Previously the setup for both the master and slave pseudoterminals was
done in TerminalWrapper::run_command.
This commit separates the relevant logic into
TerminalWrapper::setup_master_pseudoterminal
and TerminalWrapper::setup_slave_pseudoterminal.
Normally, it's the TTY layer's job to translate '\n' into the separate
'\r' and '\n' control characters needed by the terminal to move the
cursor to the first column of the next line.
(see 5d80debc1f).
In HackStudio, we directly inject data into the TerminalWidget to
display command status. This means that this automatic translation
doesn't happen, so we need to explicitly give it the '\r' too.
SPDX License Identifiers are a more compact / standardized
way of representing file license information.
See: https://spdx.dev/resources/use/#identifiers
This was done with the `ambr` search and replace tool.
ambr --no-parent-ignore --key-from-file --rep-from-file key.txt rep.txt *
(...and ASSERT_NOT_REACHED => VERIFY_NOT_REACHED)
Since all of these checks are done in release builds as well,
let's rename them to VERIFY to prevent confusion, as everyone is
used to assertions being compiled out in release.
We can introduce a new ASSERT macro that is specifically for debug
checks, but I'm doing this wholesale conversion first since we've
accumulated thousands of these already, and it's not immediately
obvious which ones are suitable for ASSERT.
