handle two-word commands with tmux

handle two-word commands with tmux

Trying to make a devshell using tmux can fail because "tmux new"
expects a single command, not a series of arguments. It does, however,
split strings in a suitable way. So you can quote the command.

The failure mode is particularly arcane, in that you end up
with a message like:

	ERROR: Unable to spawn terminal auto: \
	Execution of 'pseudo /bin/bash' failed with exit code 1:
	usage: new-session [-d] [-n window-name] [-s session-name] \
	[-t target-session] [command]

which is confusing because there's no "new-session" anywhere in
sight (that's actually "tmux new"), and because what failed to execute
wasn't either pseudo or bash.

(From OE-Core rev: f8ed7446755eeb88191e16749350efa1e7e6197c)

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>