Update androidx build sdk to 30 instead of current

This is only really useful to determine the linktype, which is the same
for "30" and "current". This has two good side-effects:
- allow modules that are part of the SDK to use these libs (avoiding a
  circular dependency)
- potentially build faster as it needn't wait for "current" to build

Bug: 184125529
Test: m nothing
Change-Id: I4a9139774d0afb03ad3d6a008f51f9e4a172df91
2 files changed