Make the instructions more efficient.

Especially when retrying steps in incremental builds, e.g. the
`banchan` command sets up `TARGET_BUILD_APPS` for the SDK build later.

Test: Try instructions and produce https://r.android.com/2955537
Bug: 323555083
Bug: 286551985
Change-Id: Ie8270fa24a9c5327730aa8170cdae65293e23381
1 file changed