Fix lunch choices for git_main

We add "trunk_staging-" for all COMMON_LUNCH_CHOICES so they are
valid in the trunk stable setup.

Bug: 307738446
Test: lunch
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:2c1fadaca2dd69202a3775847143e9771e8da30e)
Merged-In: I5baf9db894c35fd96d54207b2924d15b05266439
Change-Id: I5baf9db894c35fd96d54207b2924d15b05266439
1 file changed