This change unifies and simplifies the code paths between the Darwin and non-Darwin code to print the LLDB version information.
It also introduces a new variable in CMake LLDB_VERSION_STRING which can be used to specify custom version information.
With the LLDB_VERSION_STRING variable set to lldb-360.0.0, the -version output is:
./bin/lldb -version
lldb version 4.0.0 (lldb-360.0.0)
clang revision 286264 llvm revision 286265
This behavior is unified across all target platforms.