Remove references to non-existent directories

Fixes warnings during makefile parsing:
FindEmulator: find: `platform_testing/libraries/app-helpers/src': No such file or directory
FindEmulator: find: `platform_testing/libraries/app-helpers/src': No such file or directory

Test: builds
Merged-In: I323c3a917bf76431f222cef70771e8294607efc3
Change-Id: Ib7cac24fd68ddc5f641eee5526e9884e7ee0cf92
1 file changed
tree: f17f8233b9be1fef559560f685d87f2815445e19
  1. build/
  2. libraries/
  3. scripts/
  4. tests/
  5. utils/