Disable keystore build in the PDK

It depends on files in frameworks/base, which is not available.

Bug: 33451638
Change-Id: I88b2b3acd95c503afb3b448c9a26bc7ace9c5d58
Test: With PDK, mmma -j system/security/keystore
1 file changed
tree: b7b62dded8955d6a97a06f803be8cb5f65f36478
  1. keystore/
  2. keystore-engine/
  3. softkeymaster/
  4. MODULE_LICENSE_APACHE2
  5. NOTICE