Adding -j1 for aidl-freeze-api

bpmodify isn't safe for multi processes env because it doesn't use any
lock mechanism even with -w option(in-place change)

So, added -j1 option as a temp solution.

Bug: 190577319
Bug: 229413853
Test: run aidl-freeze-api with -j1
Change-Id: I7fabfa1224ea0bb8d71538f4c8012255df28a3e8