Fix ABI diff reporting with dist

When we're doing ABI diffing, we run something like:

  (run-abi-diff) || (echo && exit 1)

When `dist` is added, we attempt to copy out the result:

  (run-abi-diff) || (echo) && (copy && exit 1)

But this always fails, since it will always run exit 1. We really want
the parenthesis around the entire second section. This change switches
it to:

  (run-abi-diff) || (echo && (copy) && exit 1)

This matches the behavior before Iae25374fe937a0cbe8a8ddf9e23c3bc1f62bbb2a

Test: treehugger on P
Change-Id: Ic39da4d4630ee950b811ec7854d55d65c52f8661