Address syntax / error case nits

Observe some best practices in the APEX symlink
shell commands. No functional changes intended except with error
handling.

Bug: 128687472
Bug: 124106384
Bug: 122985829
Bug: 128249030
Test: make installclean / make droid / inspect one symlink
Change-Id: I099fed5ac8f25cc3911ce0e7ea2b9f74c2172193