Clean up Makefiles, remove HOST_JDK_IS_64BIT_VERSION

This builds on Darwin fine, so remove the non-standard darwin checks.

Remove HOST_JDK_IS_64BIT_VERSION, it's always true now, and this is the
only user.

Test: mmm packages/inputmethods/LatinIME/tools/dicttool:liblatinime-aosp-dicttool-host
Change-Id: I750c6baa29cf1d27a885ff064f0daf9d986db0b9