BUILD: Disable build for mac-host target

* Move disable darwin (mac) options to "fluoride_defaults".
* mac-host target is disabled across fluoride, but developer can still
  build for non-mac targets on a mac host.
* Remove vendor_libs/Android.mk that is no longer used.

Bug: 72618679
Test: make
Change-Id: Ibad9fad3df169e9c4e418a4511c42066fcb10fdc