Clean up overloading of FileExists

FileExists is used for directories and also returns false for 0-length
files. Both behaviors are a bit surprising, so split it into:

FileHasContent
DirExists

Test: Local build
Bug: 110097226
Change-Id: Ic6caf67a0c9194a44a75a5b5f1cb2a427312d8b4
1 file changed
tree: f260863fe67a55df64942abc5e028a3dc0105983
  1. common/
  2. guest/
  3. host/
  4. tests/
  5. tools/
  6. Android.bp
  7. Android.mk
  8. OWNERS