Fix handling of LLDB_VERS_GENERATED_FILE.

Summary:
This is Darwin only.

The symbol defined by ${LLDB_VERS_GENERATED_FILE} is used by
source/lldb.cpp, so anything that uses lldb.cpp (which is in
lldbBase) should also have the generated symbol. This means
that the entire process can be centralized within source/CMakeLists.txt
where lldbBase is constructed.

Additionally, the custom command should have dependencies on the
project file as well as the generation script so that if either
changes, the version file is correctly re-generated and everything
is re-linked appropriately.

* cmake/LLDBDependencies.cmake: Remove everything related to
  the generated version file from here.

* source/CMakeLists.txt: On Darwin, add the generated version
  file to the sources that make up lldbBase.  Also, create a
  custom target and make lldbBase depend on it to re-generate
  the generated file as needed.

* source/API/CMakeLists.txt: Don't need to build the generated
  version file here or use it to control linking against swig_wrapper.

* tools/lldb-server/CMakeLists.txt: Likewise.

Reviewers: dawn, sas, clayborg, zturner

Subscribers: lldb-commits

Differential Revision: http://reviews.llvm.org/D13552

llvm-svn: 249806