configure: Add missing quoting for some easy cases

configure: Add missing quoting for some easy cases

This commit adds quotes in some places which:
 * are spotted by shellcheck
 * are obviously incorrect
 * are easy to fix just by adding the quotes

It doesn't attempt fix all of the places shellcheck finds errors,
or even all the ones which are easy to fix. It's just a random
sampling which is hopefully easy to review and which cuts
down the size of the problem for next time somebody wants to
try to look at shellcheck errors.

Signed-off-by: Peter Maydell <[email protected]>
Reviewed-by: Marc-André Lureau <[email protected]>
Reviewed-by: Philippe Mathieu-Daudé <[email protected]>
Message-id: 20220825150703.4074125[email protected]