docs: Clarify Linux prerequisites
docs: Clarify Linux prerequisites

Change-Id: I80f072b58141ed10ecdf99b5fbc792227625e122
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/88240
Reviewed-by: Armando Montanez <97ef6fdb231c129ac8827d9f0c4106bfbf57f74f@google.com>
Commit-Queue: Chad Norvell <f2b1b54074a2cea3f685a7cf4fc055999c2f0cd6@google.com>

google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed