Fix pre-extracted PDKs

The PDK unzip logic does not place all the files in the same directory
it would place a zipfile, but instead inside a directory of the same
name:

  a/b/platform.zip!pdk.mk

turns into:

  a/b/platform/pdk.mk

So fix the PDK_FUISON_PLATFORM_DIR autodetection to take this into
account. Also don't create touch rules for the pre-extracted java files.

Bug: 118776469
Test: try building the PDK with PDK_FUSION_PLATFORM_ZIP set, and files extracted
Change-Id: Ib27d12aba773a5e6bd41fcbe8945a0bc31b8c281